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THE  ROTATION  PERIOD  OF  THE  SUN 


AS  DETERMINED  FROM  THE  MOTIONS  OF 
THE  CALCIUM   FLOCCULI 


BY 


GEORGE  E.  HALE  AND  PHILIP  FOX 


PUBLISHED  BY 
THE  CARNEGIE  INSTITUTION  OF  WASHINGTON 


THE  ROTATION  PERIOD  OF  THE  SUN 


AS  DETERMINED  FROM  THE  MOTIONS  OF 
THE  CALCIUM    FLOCCULI 


BY 


GEORGE  E.  HALE  AND  PHILIP  FOX 


PUBLISHED  BY 

THE  CARNEGIE  INSTITUTION  OF  WASHINGTON 
1908 


CARNEGIE  INSTITUTION  OF  WASHINGTON 
PUBLICATION  No.  93 


BALTIMORE,  MD.,  U.  S.  A. 


THE  ROTATION  PERIOD  OF  THE  SUN  AS  DETERMINED  FROM 
THE  MOTIONS  OF  THE  CALCIUM  FLOCCULI. 


The  rotation  period  of  the  Sun  has  been  determined  by  three  independent 
methods :  ( I )  from  measurements  of  the  motions  of  the  spots  in  longitude ; 
(2)  from  measurements  of  the  motions  of  the  faculse  in  longitude;  and  (3) 
from  spectroscopic  measurements  of  the  motion  in  the  line  of  sight  of  the 
approaching  and  receding  limbs.  The  first  series  of  monochromatic  photo- 
graphs of  the  Sun,  made  with  the  spectroheliograph  of  the  Kenwood  Observa- 
tory in  the  years  1892-94,  has  provided  material  for  a  new  determination  of 
the  rotation  period,  based  upon  the  motions  in  longitude  of  the  calcium 
flocculi.  Through  a  grant  from  the  Carnegie  Institution  it  became  possible 
to  undertake  the  measurement  of  these  plates  at  the  Yerkes  Observatory. 
The  results  of  this  investigation  are  contained  in  the  present  paper. 

THE  KENWOOD  SPECTROHELIOGRAPH. 

The  spectroheliograph  employed  in  the  present  investigation  is  shown  in 
plate  i,  attached  to  the  eye-end  of  the  Kenwood  refractor  of  12  inches 
(30.5  cm.)  aperture  and  18  feet  (5.49  m.)  focal  length.  It  consisted  of  a 
large  grating  spectroscope,  with  collimator  and  camera  of  3.25  inches  (8.4 
cm.)  aperture  and  42.5  inches  (108  cm.)  focal  length,  inclined  to  each  other 
at  an  angle  of  25°.  The  collimator  and  camera  objectives  were  corrected 
for  the  K  line.  A  4-inch  (10  cm.)  Rowland  plane  grating,  having  14,438 
lines  to  the  inch  (5,684  lines  to  the  cm.),  stood  at  the  intersection  of  the 
collimator  and  camera  axes.  The  spectroheliograph  was  provided  with  two 
movable  slits,  one  at  the  focus  of  the  collimator  (in  the  focal  plane  for 
K  light  of  the  Kenwood  refractor) ,  the  other  in  the  focus  of  the  camera  lens. 
Both  slits,  which  were  3.25  inches  (8.4  cm.)  in  length,  were  adjustable  in 
width  by  means  of  micrometer  screws.  They  were  attached  to  carriages 
mounted  on  steel  balls,  movable  across  the  axes  of  the  tubes,  at  right  angles 
to  the  spectral  lines.  A  photographic  plate-holder  was  supported  just  beyond 
the  camera  slit  and,  after  drawing  the  slide,  the  plate-holder  could  be  pushed 
forward  by  means  of  a  cam  until  the  surface  of  the  plate  almost  touched  the 
jaws  of  the  slit.  A  small  90°  reflecting  prism  was  attached  to  the  slit  carriage 
on  the  side  toward  the  grating,  and  by  a  suitable  combination  of  lenses  a 
portion  of  the  spectrum  could  be  viewed  without  disturbing  the  plate-holder. 
This  was  not  used  in  practice,  the  K  line  (in  the  fourth-order  spectrum) 
being  brought  on  to  the  slit  by  observing  lines  in  the  green  of  the  overlapping 
third  order  with  a  low-power,  positive  eye-piece.  The  motive  power  was 


^^»^r«>»-y/f 
i  <^  i  si 


2  THE   ROTATION    PERIOD    OF   THE    SUN    AS    DETERMINED 

supplied  by  a  specially  designed  clepsydra,  mounted  within  the  braced  frame 
of  the  spectroscope.  It  consisted  of  a  brass  cylinder  of  3  inches  (7.6  cm.) 
bore  and  6  inches  (15.2  cm.)  stroke,  supplied  with  a  three-way  valve,  per- 
mitting the  liquid  to  flow  in  at  one  end  of  the  cylinder  and  out  at  the  other. 
The  piston  had  a  cup-shaped  leather  packing,  and  the  phosphor-bronze 
piston-rod  passed  through  a  stuffing-box  in  the  upper  head.  At  the  end  of 
the  rod  a  system  of  bell-crank  levers  was  attached,  which  conveyed  the 
motion  to  the  slit  at  the  focus  of  the  camera  objective.  An  extension  of  the 
piston-rod  passed  through  a  guide  in  the  upper  frame  of  the  spectroscope, 
and  connected  with  the  first  slit  by  another  lever  system.  It  will  be  seen 
that  when  the  piston  was  set  in  motion,  the  two  slits  would  move  simul- 
taneously, and  in  opposite  directions,  the  first  slit  across  the  solar  image,  the 
camera  slit,  containing  the  K  line,  across  the  photographic  plate.  Water 
pressure  was  supplied  to  the  clepsydra  from  a  tank,  in  which  the  pressure 
was  kept  constant  by  means  of  an  automatic  pump.  In  winter,  alcohol  or 
glycerin  was  mixed  with  the  water  to  prevent  freezing.1 

This  spectroheliograph,  though  it  gave  satisfactory  photographs  of  the 
prominences  and  flocculi,  had  one  important  disadvantage  :  the  distortion  of 
the  image  resulting  from  the  motion  of  the  slits. 

In  the  equation  for  the  plane  reflection  grating 

A  =  —  (sin  6  ±  sin  w) 
n   ^ 

0  =  angle  of  diffraction, 
<o  :=  angle  of  incidence, 
A  =  wave-length  of  line  observed, 
n  =  order  of  spectrum  employed, 
d  =  distance  between  adjacent  lines  of  grating. 
Then 


n\ 

sin  6  =  —  -  ±  F  sin  w 
a 


Differentiating,  we  have 


-j  being  a  constant  for  a  given  line.2 

In  the  case  of  the  Kenwood  Observatory  spectroheliograph,  when  used  in 
photographing  an  image  of  the  Sun  51  mm.  in  diameter,  we  have 

6  (maximum)  —  14°  36'  0  (minimum)  =  13°  42' 

w  (maximum)  =  40°  54'  w  (minimum)  —  38°  42' 

du  =  51  mm. 

1  For  a  more  complete  description  of  this  spectroheliograph,  in  its  original  form,  see 
Astronomy  and  Astro-Physics,  May,  1892,  p.  407. 

2  See  Young,  Amer.  Jour.  Sci.,  November,  1880. 


PLATE  1 


THE  SPECTROHELIOGRAPH  OF  THE  KENWOOD  ASTROPHYSICAL  OBSERVATORY,  CHICAGO. 


FROM    THE   MOTIONS   OF   THE   CALCIUM    FLOCCULI.  3 

Substituting  in  ( I ) ,  we  find  dO  =  39.8  mm.  That  is,  the  diameter  of  the 
photographed  solar  image  which  is  parallel  to  the  length  of  the  spectrum  will 
be  reduced  by  the  distortion  from  51  mm.  to  39.8  mm.  The  diameter  parallel 
to  the  lines  of  the  spectrum  will  of  course  remain  undistorted.  This  result, 
however,  is  only  approximate,  as  the  distortion  for  equal  values  of  dot 
increases  from  one  side  of  the  image  to  the  other.  Thus  if  we  make 
da>  =  i  mm.,  and  calculate  the  values  of  dO  for  one  side,  the  center  and  the 
other  side  of  the  solar  image,  we  obtain  the  respective  values 

dO  =  0.78  mm.  (for  maximum  value  of  6) 
dO  =  0.79  mm.  (for  mean  value  of  6) 
dO  =  0.80  mm.  (for  minimum  value  of  0) 

In  measuring  photographs  distorted  in  this  way  the  necessary  correction 
for  a  point  at  a  given  distance  from  the  Sun's  limb  might  be  taken  from  a 
table,  readily  constructed  for  a  given  position  of  the  Sun's  image  with  respect 
to  the  axis  of  the  collimator.  To  define  this  position,  means  were  provided 
for  making  the  solar  image  concentric  with  the  axis  of  the  collimator.  Care 
was  always  taken  to  orient  the  image  so  that  the  distorted  axis  should  be 
parallel  to  the  solar  equator  in  the  photograph.  For  this  purpose  the  whole 
instrument  could  be  rotated  about  the  axis  of  the  collimator,  the  direction  of 
the  slit  being  read  off  on  a  position  circle.  The  parallel  lines  on  the  photo- 
graph (due  to  dust  on  the  slit,  which  can  not  be  altogether  avoided  in  any 
form  of  spectroheliograph  when  the  slit  is  narrow)  were  made  to  serve  a 
useful  purpose  in  the  orientation  of  the  image. 

After  a  considerable  number  of  distorted  photographs  had  been  taken  with 
the  instrument,  a  simple  device  was  attached  for  the  purpose  of  making  the 
images  practically  circular  in  form.  This  consisted  of  a  lever  arm  which 
moved  the  photographic  plate,  during  the  exposure,  in  a  direction  opposite 
to  that  of  the  motion  of  the  second  slit,  and  through  a  distance  equal  to  the 
difference  between  the  major  and  minor  axes  of  the  distorted  image.  It  will 
be  observed  that  this  correction,  though  not  perfect,  is  very  nearly  so.  The 
modified  instrument  yielded  photographs  which  were  very  nearly  circular 
in  form.8 

The  Kenwood  spectroheliograph  and  all  the  optical  parts  of  the  Kenwood 
refractor  were  constructed  by  Brashear,  whose  valuable  services  and  cordial 
cooperation  greatly  facilitated  the  investigations  of  the  Observatory.  Warner 
&  Swasey  also  gave  much  useful  assistance,  in  addition  to  their  work  of 
constructing  the  telescope  mounting  and  dome. 

During  the  years  1892-94  there  were  obtained  with  the  Kenwood  spectro- 
heliograph 2,295  photographs  of  the  Sun  showing  the  calcium  flocculi.  In 
1,408  of  these  photographs  the  image  was  elliptical  (or  approximately  so) 

*A  mechanical  device  for  copying  distorted  photographs,  in  such  a  way  as  to  obtain 
a  circular  image,  was  also  constructed  at  the  Kenwood  Observatory. 


THE   ROTATION    PERIOD    OF   THE    SUN    AS    DETERMINED 


in  form.  These  were  obtained  before  the  device  for  correcting  the  distortion 
of  the  image  had  been  applied  to  the  spectroheliograph.  By  means  of  the 
apparatus  devised  for  the  purpose,  these  negatives  might  have  been  copied 
in  such  a  way  as  to  give  circular  images,  in  which  case  they  would  have  been 
available  for  the  present  investigation.  But  in  view  of  the  much  greater 
excellence  of  the  photographs  which  were  being  obtained  with  the  4O-inch 
Yerkes  Observatory  telescope,  when  the  present  reduction  of  the  Kenwood 
plates  was  undertaken,  it  was  decided  to  confine  the  work  to  the  measurement 
of  the  circular  images,  887  of  which  were  available.  Mention  has  not  yet 
been  made  of  the  slight  distortion  of  the  Sun's  image,  caused  by  the  curvature 
of  the  spectrum  lines  in  the  Kenwood  spectroheliograph.4  Since  the  motion 
of  the  photographic  plate,  which  served  to  transform  the  elliptical  image  into 
a  nearly  circular  one,  did  not  also  furnish  the  means  of  correcting  for  the 
curvature  of  the  slit,  precautions  had  to  be  taken,  while  making  the  photo- 
graphs, to  eliminate  the  effect  of  this  curvature.  For  this  reason,  the  plates 
were  made  in  two  series,  in  one  of  which  the  slits  were  made  parallel  to  the 
Sun's  axis,  while  in  the  other  they  were  placed  in  a  position  angle  90°  from 
this.  For  the  present  investigation  the  plates  of  the  first  series  were 
employed,  since  the  displacement  (due  to  curvature)  of  the  flocculi  in  longi- 
tude would  be,  in  this  case,  only  a  second-order  effect,  too  small  to  be 
appreciable  in  photographs  no  sharper  than  those  available.  In  order  to 
avoid  errors  in  the  identification  of  the  flocculi  measured,  no  attempt  was 
made  to  employ  plates  separated  by  two  or  more  cloudy  days.  The  best  plate, 
corresponding  to  each  day  in  a  series  of  two  or  more  clear  days,  was  selected 
for  measurement.  In  this  way  the  number  of  plates  to  be  measured  was 
reduced  to  138,  covering  the  period  1893  July  31  to  1894  September  29. 


*  Radius  of  curvature  =  about  I  m. 


Condensing 


Plate 


ia"lens 


Globe 


FIG.  i.     PLAN  AND  ELEVATION  OF  THE  GLOBE  MEASURING  MACH 


FROM    THE    MOTIONS    OF    THE    CALCIUM    FLOCCULI. 


METHOD  OF  MEASUREMENT. 

Two  causes  made  it  undesirable  to  adopt  the  ordinary  method  of  measure- 
ment in  the  reduction  of  these  photographs.  In  the  first  place,  the  high 
degree  of  precision  attainable  in  measuring  very  sharp  direct  photographs  of 
the  Sun,  such  as  those  comprised  in  the  Greenwich  series,  is  out  of  reach  in 
the  case  of  photographs  taken  with  such  an  instrument  as  the  Kenwood 
spectroheliograph.  In  the  second  place,  the  measurement  and  reduction  by 
the  ordinary  process  of  the  numerous  positions  required  would  have  been  a 
larger  task  than  could  be  undertaken  in  the  intervals  of  work  with  the 
Rumford  spectroheliograph.  Accordingly  a  new  method  of  measurement 
was  devised  by  Mr.  Hale,  which  is  at  once  exceedingly  rapid  in  execution 
and,  at  the  same  time,  sufficiently  precise  for  the  immediate  object  in  view.5 

The  photographs  are  projected  by  means  of  the  light  of  an  electric  arc 
lamp  upon  a  globe  accurately  ruled  with  a  series  of  meridians  and  parallels. 
The  details  of  the  arrangement  are  described  below.  The  greater  part  of  the 
apparatus  was  constructed  in  the  instrument  shop  of  the  Yerkes  Observatory 
(see  fig.  i).  References  to  this  apparatus  will  be  used  as  follows : 

A  =  Arc  lamp,  fed  by  clock-work  so  as  to  keep  the  arc  at  a  fixed  point. 

C  =  Condensing  lens,  10  inches  (25.4  cm.)  in  diameter. 

P  =  Plate-holder,  which  carries  the  solar  negative. 

L  =  12-inch  (30.5  cm.)  objective  of  18  feet  (5.49  m.)  focal  length, 

which  forms  an  image  of  the  photograph  upon  the  globe,  G. 
M  =  Plane  mirror  inserted  in  the  path  of  the  rays,  to  secure  the  neces- 
sary distance  of  the  globe  from  the  lens,  in  the  limited  space 
available.     The  globe  must  subtend  an  angle  of  32'  as  seen 
from  the  lens. 

THE  GLOBE. 

The  globe  is  of  cast-iron,  accurately  turned 
to  form  a  sphere  9.53  inches  (24.21  cm.)  in 
diameter.  It  was  enameled  white  to  receive  the 
ruling,  and  afterwards  reworked  to  a  spherical 
form.  In  order  to  rule  the  parallels  of  latitude, 
centers  were  drilled  at  points  corresponding  to 
the  north  and  south  poles,  and  the  globe  was 
mounted  in  a  Brown  &  Sharpe  milling  machine, 
between  the  spindle  and  the  overhanging  arm. 
A  support  for  a  ruling-pen  was  clamped  to 
the  spiral  head,  the  pen  resting  on  the  globe. 
The  position  of  the  equator  was  determined  by 

5  For  an  improved  form  of  globe-measuring  machine  (the  Heliomicrometer),  capable 
of  giving  results  of  the  highest  precision,  see  Contributions  from  the  Solar  Observa- 
tory, No.  16 ;  Astrophysical  Journal,  June,  1907. 


Plane  mirror 


6  THE   ROTATION    PERIOD    OF    THE    SUN    AS   DETERMINED 

careful  measurement  and  ruled  by  rotating  the  globe.  The  support  carrying 
the  pen  was  then  moved  through  i°  by  means  of  the  index  plate,  and  the 
parallel  was  drawn  by  again  rotating  the  globe.  After  the  parallels  to  60° 
north  and  south  had  been  ruled  in  this  way,  those  at  5°,  10°,  15°,  etc.,  were 
slightly  strengthened;  the  parallels  marking  the  10°  zones,  viz.:  10°,  20°, 
30°,  etc.,  were  still  further  strengthened  to  facilitate  the  readings. 

To  rule  the  meridians,  the  globe  was  mounted  on  the  cross-table  of  the 
milling  machine,  with  the  centers  again  at  the  poles,  and  was  clamped  to  the 
spiral  head,  so  that  it  might  be  rotated  through  any  desired  angle  by  means 
of  the  index  plate.  The  pen  was  mounted  on  an  arm,  permitting  it  to  be 
moved  in  a  great  circle  from  pole  to  pole.  The  first  line  ruled,  which  we 
shall  subsequently  call  the  central  meridian,  was  carefully  located  midway 
between  the  centers  on  which  the  globe  was  ultimately  to  rest.  These  had 
been  drilled  at  points  on  the  globe  exactly  90°  from  the  poles.  Hence,  this 
axis  passes  through  the  globe  as  a  diameter  in  the  equatorial  plane.  After 
the  principal  meridian  had  been  ruled,  by  moving  the  pen  from  pole  to  pole, 
the  other  meridians  were  successively  ruled  at  i°  intervals,  accurately 
determined  by  means  of  the  index  plate.  As  in  the  case  of  the  parallels  of 
latitude,  the  meridians  marking  the  multiples  of  5°  in  longitude  were  strength- 
ened, and  those  at  10°,  20°,  30°,  etc.,  were  made  still  heavier. 

The  ruled  globe  was  mounted  as  shown  in  plate  2.  When  supported  in 
this  way,  any  motion  of  rotation,  producing  a  change  in  the  inclination  of 
the  globe's  axis,  corresponds  to  a  change  in  the  inclination  of  the  Sun's  axis 
with  reference  to  the  ecliptic.  With  the  aid  of  an  index  moving  over  a 
divided  arc,  the  globe  may  be  set  so  that  the  heliographic  latitude  of  the 
center  of  the  globe  corresponds  to  that  of  the  Sun's  center  on  the  day  when 
the  photograph  to  be  measured  was  taken. 

The  globe  and  support  can  be  moved  on  rails  toward  or  from  the  pro- 
jecting lens,  so  that  the  varying  diameter  of  the  solar  image,  at  different 
seasons,  can  be  made  to  correspond  with  the  diameter  of  the  globe.  The 
entire  apparatus  rests  on  a  strong  shelf,  supported  on  brackets  from  a  brick 
wall  in  the  basement  of  the  Yerkes  Observatory. 

PLATE-HOLDER. 

The  plate-holder,  fig.  2,  is  provided  with  spring  clips  for  holding  the  plate 
firmly  in  position.  The  disk  which  carries  the  plate  may  be  rotated  in  a  plane 
perpendicular  to  the  beam  of  light,  the  orientation  of  the  plate  being  read  on 
a  divided  arc.  The  Kenwood  spectroheliograph  could  be  rotated  so  that  the 
motion  of  the  slits  in  the  instrument  was  parallel  to  the  Sun's  axis  for  the 
date  on  which  the  photograph  was  made.  With  this  adjustment  of  the 
instrument,  which  was  always  made  for  plates  of  the  first  series,  a  line  drawn 
upon  the  plate  by  a  needle  crossing  the  first  slit  may  always  be  taken  to 
correspond  with  the  direction  of  the  Sun's  axis.  By  clamping  the  plate  in 


FROM    THE   MOTIONS   OF   THE   CALCIUM    FLOCCULI.  7 

the  holder,  so  that  the  line  corresponds  with  the  zero  of  the  scale,  the  position- 
angle  of  the  Sun's  axis  is  accounted  for.8  The  plate-holder  is  mounted  in  a 
fixed  position  on  a  shelf  just  behind  and  above  the  globe,  and  has  no  motion 
in  the  direction  of  the  beam.  Two  motions  are  provided  for  centering  the 
image  on  the  globe.  The  east  and  west  setting  is  accomplished  by  moving 
the  plate-holder  toward  or  away  from  the  wall,  while  the  north  and  south 
motion  is  produced  by  raising  or  lowering  the  plate-holder  in  its  supporting 
frame  by  means  of  a  double  wedge.  The  centering  of  the  image  is  done  on 
a  fixed  screen,  mounted  in  front  of  the  globe,  as  shown  in  plate  2.  The 


FIG.  2.    THE  PLATE-HOLDER. 

position  of  the  plate-holder  is  such  that  it  may  be  adjusted  by  the  operator 
while  he  is  observing  the  globe,  thus  rendering  the  centering  a  simple 
matter.  The  operation  of  mounting  the  plate  in  the  plate-holder,  the  setting 
of  the  globe  and  the  orientation  of  the  image,  occupies  from  5  to  10  minutes. 

PROJECTING  LENS. 

The  lens  L,  which  is  used  to  form  an  image  of  the  plate  on  the  globe,  is  a 
12-inch  (30.5  cm.)  photographic  objective,  of  18  feet  (5.49  m.)  focal  length, 
which  was  formerly  used  with  the  Kenwood  telescope.  The  position  of  the 

6 The  Rumford  spectroheliograph  can  not  be  rotated;  but  the  dust-lines  show  the 
direction  of  the  plate's  motion  (north  and  south).  In  measuring  photographs  made 
with  this  instrument,  the  plates  are  clamped  with  the  dust-lines  parallel  to  the  zero 
line  on  the  disk,  after  which  the  disk  is  rotated  through  an  angle  equal  to  the  position- 
angle  of  the  Sun's  axis,  for  the  day  on  which  the  plate  was  taken. 


8  THE   ROTATION    PERIOD    OF   THE    SUN    AS    DETERMINED 

lens,  between  the  plate-holder  and  the  globe,  is  necessarily  dependent  upon 
the  position  of  the  globe  itself.  Since  the  globe  must  be  moved  to  correspond 
with  the  change  in  diameter  of  the  solar  image,  the  lens  is  correspondingly 
moved  by  an  amount  such  as  to  retain  the  plate  and  globe  in  the  conjugate 
foci  of  the  lens. 

Theoretically,  the  angular  diameter  of  the  globe,  as  seen  from  the  lens, 
should  be  the  same  as  the  angular  diameter  of  the  Sun  as  seen  from  the 
Earth.7  This  would  place  the  globe  at  a  distance  of  about  84.26  feet 
(25.68  m.)  from  the  projecting  lens.  Since  the  diameter  of  the  image  on  the 
Kenwood  plates  is  2  inches  (50.8  mm.),  when  the  angular  diameter  of  the 
Sun  is  32',  the  lens  should  have  a  focal  length  of  about  14.84  feet  (4.51  m.), 
in  order  that  the  projected  image  may  correspond  in  diameter  with  the  globe. 
No  lens  of  this  focal  length,  and  of  sufficiently  large  aperture,  was  available, 
and  accordingly  the  1 2-inch  objective  was  employed.  As  the  distance  of  the 
globe  from  this  lens  was  103.8  feet  (31.64  m.),  a  small  error  enters  into  the 
measurements.  In  the  triangle,  Sun's  center,  flocculus,  Earth,  we  have  intro- 
duced an  error  in  the  angle  at  the  Earth  usually  designated  sr  or  p. 

This  angle  /  enters  into  the  solution  of  the  solar  triangle,  pole,  flocculus, 
center  of  the  disk,  as  a  correction  in  the  arc,  flocculus,  center  of  the  disk, 
usually  called  ^  or  p,  and  at  the  limb,  has  its  maximum  value  of  16'.  In  our 
case  $1  is  smaller,  having  a  maximum  value  of  13.1'.  That  is,  every  point 
would  appear  to  be  slightly  shifted  toward  the  center  of  the  globe.  Even  in 
the  case  of  the  maximum  difference  the  error  is  inappreciable.  In  order  to 
avoid  the  errors  always  incident  to  measures  of  objects  lying  near  the  limb 
in  solar  photographs,  the  measures  of  the  present  series  of  plates  have  been 
confined  to  regions  lying  within  45°  of  the  central  meridian.  On  account  of 
the  rarity  of  occurrence  of  large  flocculi  in  high  heliographic  latitudes,  it  was 
unnecessary  to  set  a  limit  in  the  direction  north  and  south.  In  the  extreme 
cases,  where  the  measured  position  is  45°  east  or  west  of  the  central  meridian, 
and  45°  north  or  south,  the  difference  between  the  true  s'  and  our  erroneous 
value  is  s'  —  s^'  =  2.4'.  Had  this  difference  been  appreciable,  it  might  have 
been  eliminated  for  the  region  in  which  the  measures  are  confined  by  slightly 
enlarging  the  circle  on  the  screen  in  front  of  the  globe,  with  which  the  image 
is  always  made  to  coincide. 

ARC  AND  CONDENSING  LENS. 

The  arc  and  condensing  lens  are  inclosed  in  a  small  room,  in  order  that  the 
general  illumination  on  the  globe  may  be  minimized.  As  already  remarked, 
the  arc  is  of  the  focusing  type,  with  inclined  carbons.  The  condenser  is  a 
plano-convex  lens,  10  inches  in  diameter. 

7  The  theory  of  the  globe-measuring  machine  will  be  published  in  a  subsequent  paper. 


PLATE  2. 


FROM    THE    MOTIONS    OF    THE    CALCIUM    FLOCCULI.  9 

ADJUSTMENTS. 

The  principal  adjustments  are  as  follows : 

(1)  The  plate  should  be  normal  to  the  line  joining  center  of  globe  and  center  of 

plate. 

(2)  The  12-inch  projecting  lens  should  be  collimated  in  this  line. 

(3)  The  rails  on  which  the  globe  slides  should  be  parallel  to  this  line. 

(4)  The  axis  of  the  globe  must  be  adjusted  in  azimuth  (perpendicular  to  the  line  of 

collimation)   and  leveled  so  that  a  straight  perpendicular  line  on  the  plate 
can,  in  projection,  be  made  to  coincide  with  the  central  meridian. 

(5)  When  the  globe  is  so  adjusted,  through  rotation  on  its  axis,  that  a  horizontal  line 

on  the  plate,  in  projection  on  the  globe,  coincides  with  the  equator,  the  index 
which  gives  the  inclination  of  the  Sun's  axis  must  read  zero. 

PROCESS  OF  MEASUREMENT. 

The  operations  to  be  carried  out  in  measuring  a  plate  are  as  follows :  The 
plate  is  mounted  in  the  plate-holder,  so  that  the  line  parallel  to  the  solar  axis 
corresponds  approximately  with  the  zero  of  the  scale.  The  arc  is  started, 
and  the  accurate  adjustment  for  position-angle  is  made  by  rotating  the  plate 
until  the  projected  line  coincides  with  the  central  meridian  of  the  globe.  The 
axis  of  the  globe  is  then  inclined  so  as  to  make  the  heliographic  latitude  of 
the  center  of  the  disk  correspond  with  that  of  the  center  of  the  Sun's  disk 
on  the  day  in  question.  The  image  is  then  centered  in  the  circle  on  the 
screen,  the  globe  is  moved  until  the  image  falls  exactly  within  the  circle,  and 
the  projecting  lens  is  moved,  if  necessary,  to  preserve  the  focus.  In  measur- 
ing the  flocculi  the  image  is  received  upon  a  small  white  card,  from  which 
it  is  dropped  upon  the  globe  by  rapidly  moving  the  card  aside.  As  the  card 
is  free  from  the  lines  ruled  on  the  globe,  the  image  can  be  seen  upon  it  to 
better  advantage.  The  positions  of  the  points  in  heliographic  latitude  and 
longitude  from  the  central  meridian  are  read  off  directly,  by  estimation,  to 
the  nearest  tenth  of  a  degree. 

The  identification  of  points  to  be  measured  requires  much  care,  in  view  of 
the  complexity  of  the  changes  of  form  of  the  flocculi.  Prints  from  the 
original  negatives  were  made  on  "  Velox  "  paper,  and  all  measured  points 
were  carefully  marked.  By  comparison  of  the  prints,  the  points  can  be 
followed  from  day  to  day,  thus  assuring  certain  identification.  The  flocculi 
change  in  form  rather  rapidly,  but  a  number  of  points  were  followed  for  four, 
five,  and  six  days.  Of  the  1,213  points  measured,  647  correspond  to  inter- 
vals of  one  day;  331,  to  two  days;  137,  to  three  days;  65,  to  four  days;  26, 
to  five  days ;  and  7,  to  six  days.  The  positions  of  all  points  were  estimated 
to  a  tenth  of  a  degree. 


10       THE  ROTATION  PERIOD  OF  THE  SUN  AS  DETERMINED 

SOURCES  OF  ERROR. 

In  considering  the  many  sources  of  error  that  may  affect  our  results,  the 
character  of  the  photographs  must  always  be  borne  in  mind.  The  small  size 
of  the  solar  image;  the  lack  of  sharpness  of  the  flocculi ;  and  their  rapid 
changes  of  form,  making  identification  of  points  for  measurement  very  diffi- 
cult, all  tend  to  reduce  the  accuracy  of  the  results.  As  compared  with  such 
investigations  as  those  of  Stratonoff  on  the  motion  of  the  faculse,  however, 
we  have  two  important  advantages  which  reduce,  if  they  do  not  completely 
offset,  the  disadvantages  arising  from  the  above  causes.  These  include : 

(1)  The  possibility  of  making  all  measures  near  the  center  of  the  disk,  instead  of 

near  the  limb. 

(2)  The  greater  number  of  objects  available  for  measurement,  and  the  consequent 

better  distribution  of  the  points  in  latitude.8 
The  following  sources  of  error  must  be  considered : 

(1)  Distortion  of  the  solar  image,  arising  from — 

(a)  The  different  rates  of  motion  of  the  first  and  second  slits  (p.  3).    This  is 
corrected,  with  sufficient  exactness  for  the  present  work,  by  the  motion  of 
the  photographic  plate  during  the  exposure. 

(b)  Errors  in  centering  the  solar  image  on  the  first  slit.    It  is  evident  from  the 
equation  of  the  grating  that  the  degree  of  the  distortion  of  the  image  depends 
on  its  position  with  respect  to  the  axis  of  the  collimator.     For  any  slight 
deviations  of  the  solar  image  from  the  central  position,  however,  the  effect 
is  small,  and  much  less  than  that  due  to  (a). 

(c)  Curvature  of  the  second  slit.     When  taking  the  photographs,  the  effect  of 
curvature  was  reduced  to  an  inappreciable  quantity  of  the  second  order  by 
setting  the  slit  in  all  cases  parallel  to  the  solar  equator.     The  latitudes  are 
thus  mainly  (though  but  slightly)   affected,  while  the  longitudes  suffer  only 
in  the  second  order. 

(2)  Errors  of  globe  divisions.     These  were  found  on  examination  to  be  so  small 

that  they  could  safely  be  neglected. 

(3)  Care  was  always  taken  in  the  orientation  of  the  image  and  in  centering  it  on 

the  globe.  The  accidental  errors  arising  from  these  sources  were  undoubt- 
edly small. 

(4)  The  focal  length  of  the  only  lens  of  sufficient  aperture  available  for  the  projec- 

tion of  the  solar  photograph  on  the  globe  was  18  feet  (5.49  m.)  instead  of 
14.8  feet  (4.51  m.),  required  by  theory.  The  errors  due  to  this  cause  have 
been  shown  to  be  inappreciable. 

8  This  applies  particularly  to  well-defined  images,  in  which  the  minute  flocculi  are 
shown. 


FROM    THE    MOTIONS    OF    THE    CALCIUM    FLOCCULI.  11 

ROTATION  PERIODS  DERIVED  FROM  THE  MEASURES. 

About  3,000  measures  were  obtained,  of  1,213  points  in  the  flocculi.  The 
actual  heliographic  longitudes  of  the  flocculi  were  not  measured,  but  only 
their  differences  in  longitude  east  or  west  of  the  central  meridian.  The  lati- 
tudes of  all  the  points  were  measured ;  but  they  are,  of  course,  affected  by  the 
slight  error  due  to  curvature  of  the  second  slit.  This  does  not  exceed  0.6° 
in  the  extreme  case  and  affects  only  the  grouping  of  the  different  flocculi 
into  zones  in  taking  the  mean  value  for  each  zone.  As  the  spectroheliograph 
was  sometimes  oriented  with  the  convex  side  of  the  curved  second  slit  north 
and  sometimes  with  the  convex  side  south  the  error  of  grouping  will  be 
practically  self-compensating. 

In  gathering  together  the  different  measures  of  the  same  point,  to  determine 
the  rotation  period,  the  first  reading  was  taken  as  zero  degrees,  and  the 
others  reduced  accordingly.  The  readings  thus  assembled  are  given  in  table 
i.  It  has  not  seemed  necessary  to  publish  all  the  measures  from  the  original 
note-book.  The  plate  number  and  date  are  given  in  the  first  column.  The 
second  column  contains  the  flocculus  number,  as  marked  on  the  enlarged 
prints  for  the  purpose  of  identification.  The  third  column  gives  the  zone  in 
which  the  flocculus  was  found:  a  =  o°  to  5°  ;  b  =  o°  to  — 5°  ;  c  =  5°  to 
io°;d  =  —5°  to  —10° ;  e  =  10°  to  15° ;  /  =  — 10°  to  —15° ;  g  =  15°  to 
20°  ;  h  =  — 15°  to  —20°,  etc. 

The  sixth,  seventh,  eighth,  ninth,  tenth,  and  eleventh  columns  show  the 
movement  in  longitude  during  the  days,  or  portions  of  days,  intervening 
between  the  first  and  second  plates,  first  and  third,  first  and  fourth,  etc.,  of 
the  flocculus  in  question.  The  fourth  column  gives  the  angular  movement 
per  day,  as  derived  graphically  from  the  readings,  by  platting  the  times  as 
abscissae,  and  the  difference  in  longitude  as  ordinates.  The  rise  of  the  line 
which  best  represents  the  observations,  during  an  interval  of  24  hours,  is 
the  desired  angular  movement. 

The  cross-section  paper  employed,  for  which  we  are  indebted  to  Mr.  Abbot, 
was  specially  ruled  with  great  accuracy  for  the  Smithsonian  Astrophysical 
Observatory.  The  paper  is  ruled  in  millimeters,  and  the  scale  of  platting 
is  such  that  5  mm.  correspond  to  i  hour  in  the  abscissae,  and  single  milli- 
meters to  o.i  °  in  the  ordinates.  Heavy  lines  were  ruled  to  correspond  with 
the  even  24  hours,  and  these  were  taken  to  represent  the  noon  hour.  The 
times  of  the  plates  were  laid  off,  so  many  hours  and  minutes,  right  or  left 
from  this  line,  depending  upon  whether  the  plate  was  taken  in  the  afternoon 
or  forenoon.  The  first  ordinate  was  o,  the  second  approximately  13°,  etc., 
as  given  in  columns  6,  7,  8,  9,  10,  and  n.9 

Let  y19  y2,  y3,  .  .  .  .  represent  the  observed  motions  in  longitude,  corre- 
sponding to  the  times  f±,  t2,  fa,  .  .  .  .  In  general  tit  t2,  t3,  .  .  .  .  are  not 

9  The  graphical  method  described  below  is  due  to  Dr.  Frank  Schlesinger. 


12  THE    ROTATION    PERIOD    OF    THE    SUN    AS    DETERMINED 

exact  multiples  of  24  hours.  In  the  case  where  we  have  three  observations 
connect  y±  and  y3,  and  let  A±  and  A3  represent  the  values  of  the  longitude 
corresponding  to  the  intersections  of  this  line  with  the  noon  lines  of  the 
first  and  third  days.  Similarly  A2  is  given  by  the  intersection  of  the  line 
joining  y±  and  y2  with  the  noon  line  of  the  second  day.  In  the  case  of  four 
observations,  the  values  of  A±,  A2,  A3,  A4  are  given  by  the  intersections  with 
the  corresponding  noon  hours  of  the  lines  joining  y±  and  y4,  and  y2  and  y3. 
Treat  A1?  A2,  A3,  ....  as  observed  quantities,  and  call  A0  the  value  of  the 
longitude  corresponding  to  zero  time.  By  the  method  of  least  squares,  the 
equations 

A0  —  A!  =  o  A0  +  x  —  A2  =  o  A0  +  2.x  —  A3  =  o 

give  at  once 

3*0  +  3*—  (AI  +  A2  +  A3)  =  o  3A0  +  5*—  (A2  +  2A3)  =  o 

whence 


Thus,  in  the  case  of  observations  made  on  three  successive  days,  the 
position  of  the  middle  point  does  not  affect  the  result;  for  in  approaching 
the  thread  (which  was  used  in  place  of  drawing  lines)  to  the  middle  observa- 
tion, the  inclination  is  not  changed.  This  is,  of  course,  absolutely  true  only 
when  the  intervals  are  accurately  equal  to  24  hours,  but  it  is  a  sufficiently 
close  approximation  in  our  observations.  The  error  does  not  exceed  0.05° 
under  ordinary  conditions  and  0.1°  in  a  few  extreme  cases. 

For  four  consecutive  days  we  obtain 


The  second  form  here,  as  in  the  following  cases,  gives  the  weight  assigned 
to  the  line  through  the  extreme  observations  and  to  that  through  the  inter- 
mediate ones. 

In  case  the  second  day's  observation  is  lacking 

r--2  (\         \  ^         l   f\         \  \       l  $*  /A4  —  A^      A3  —  A 
—  (A.-AJ     --(A,  -A,)    =-|6(^—  —  )  +  —  — 

If  the  third  day's  observation  is  lacking 

4       A  A        A4       A 


—  2  (\         \  \  _\     I    (\         \  \  __  I 

-?(x<        H-(*.-A.)  -7 


2 

For  five  consecutive  observations  the  middle  one  disappears,  as  in  the  case 
of  three,  and  we  find 

A4       A2 


FROM    THE    MOTIONS    OF    THE    CALCIUM    FLOCCULI.  13 

With  A2  or  A4  missing,  the  solutions  are  similar,  but  too  complex  to  be  of 
value  in  platting. 

If  A2  and  A3  are  lacking,  we  find 


If  A3  and  A4  are  lacking 


Fig.  3  illustrates  the  graphical  solution  of  the  observations  of  Flocculus  No. 
737.  The  observations  were  made  on  plates  No.  3106,  1894,  Mar.  14,  ih59m; 
No.  3112,  1894,  Mar.  15,  ihi2m;  No,  3117,  1894,  Mar.  16,  2h44m;  and  No. 
3121,  1894,  Mar.  17,  I2h04m. 

7i  =0  y2  =  12.7  y3  =  26.2  y4  =  38.7 

A!  =  —1.10°  A2  =  12.07°  ^3  =  24.76°  A4  =  38.68° 

x  =  ^  (A4  —  A,)  +  -L  (A3  —  A2)  =  13.203 

Or,  extending  the  line  A2A3  for  the  three  days,  it  intersects  the  noon  lines 
on  the  first  and  fourth  days  at  a  and  (3.  Now,  knowing  that  the  line  AXA4 
has  nine  times  the  weight  of  A2A3,  we  may  make  a  reading  on  A±a  one-tenth 
the  distance  from  A±  toward  a  =  —  1.05°  and  on  A4/?  one-tenth  the  distance 
from  A4  toward  (3  =  38.56 

1.05 
-^=13.203 


o 

Or,  as  is  most  frequently  done  in  practice,  we  may  draw  a  third  line  A^ 
parallel  to  A2A3  passing  through  A1. 

Again  read  on  A48  one-tenth  the  distance  from  A4  toward  8  =  38.50 

38.50+  1.  10 
*:=—  -=13.200 

o 
In  case  we  use  the  general  formula  and  express  ^,  t2,  ts,  t4,  in  minutes, 

_T      * 

*- 


k  =  the  number  of  observations,  in  this  case  4, 
we  find 

x—  13.183 


14  THE   ROTATION    PERIOD    OF    THE    SUN    AS    DETERMINED 


30 


2-5 


20 


15 


10 


30 


25 


20 


15 


10 


FIG.  3.    GRAPHICAL  INTERPOLATION  METHOD. 


FROM    THE    MOTIONS    OF   THE    CALCIUM    FLOCCULI. 


15 


TABLE  i.    Diurnal  Motions  of  the  Flocculi. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

i 

2 

3 

4 

5 

6 

No.  2401 

I 

C 

14-74° 

I3.780 

12.6 

26.6 

39-9 

1893,  July  31 

19 

C 

14.84 

13-88 

11.7 

25-9 

39-7 

2*127111 

5 

e 

14.03 

13.07 

10.6 

24.6 

5' 

e 

14.42 

13-47 

10.8 

25.0 

38.5 

4' 

e 

14.38 

13.42 

10.8 

18 

f 

14.26 

13.31 

10.  1 

25.1 

23 

g 

14.06 

13.10 

10.7 

24.3 

37-4 

5i.o 

2' 

e 

14.42 

13.47 

10.9 

24.5 

38.2 

52.5 

14 

h 

I3./8 

12.82 

10.3 

15 

h 

13.89 

12.93 

10.  1 

24.3 

ii 

j 

12.67 

11.72 

9.4 

V 

k 

13.64 

12.68 

27.7 

36  i 

8' 

I 
I 

J-O.VMt 

12.  6l 
12.  6l 

11.65 
11.66 

9.9 
9.3 

-**o  *o 
21.6 

ov- 

16 

I 

13.54 

12.58 

9.9 

23.7 

16' 

I 

13.19 

12.23 

9.8 

23.1 

No.  2407 

i' 

c 

14.62 

13.67 

13.6 

27.0 

41.8 

1893,  Aug.  i 

27 

d 

14.42 

13.47 

14.0 

27.2 

41.0 

Qh34m 

26' 

f 

14.41 

13.45 

14.5 

26 

h 

12.54 

11.58 

12.  1 

3 

i 

14.59 

13.64 

14.2 

27.3 

42.0 

6 

i 

14.29 

13-33 

I4.I 

27.3 

22 

j 

12.07 

ii.  ii 

13.8 

26.7 

40.3 

6' 

k 

14.07 

13.12 

13.7 

26.0 

No.  2421 

32 

b 

13.99 

13.04 

12.6 

1893,  Aug.  2 

_  ./ 

b 

14.72 

13.76 

13.6 

27.3 

nh30m 

38 

b 

15.24 

14.29 

13.8 

36' 

b 

13.81 

12.85 

12.5 

25.5 

36" 

b 

14.26 

13-30 

13-7 

26.4 

37' 

c 

14.37 

13-41 

13.3 

26.6 

39.7 

36 

d 

14.62 

13.66 

13.6 

27.1 

33 

e 

14.78 

13.82 

12.8 

27.4 

4 

i 

14.71 

13-75 

13.2 

27.3 

29 

i 

14.49 

13.54 

12.9 

26.9 

30 

i 

14.06 

13.10 

12.7 

26.0 

No.  2429 

35 

d 

15.87 

14.92 

15.4 

30.1 

48.7 

1893,  Aug.  3 

47' 

h 

14.22 

13.26 

13.3 

26.7 

43.4 

5L9 

I0h42m 

30' 

i 

14.66 

13.70 

13.9 

29' 

i 

14.66 

13.70 

13.9 

47 

j 

13.71 

12.75 

13.1 

25.8 

43.9 

38' 
38" 

I 
I 

13.09 
14.35 

12.13 
13-39 

12.3 

13.6 



44-4 

53-4 

66.7 

No.  2442 

38'" 

b 

14.57 

13.62 

13.3 

1893,  Aug.  4 

52 

b 

14.75 

13-79 

13.9 

31-7 

40.9 

54-5 

69.2 

nh7m 

53' 

b 

14.73 

13-77 

13.5 

55 

b 

14.68 

13.72 

13.8 

3L5 

40.7 

54-1 

69.0 

5i 

d 

14.69 

13.73 

14.2 

31.2 

40.8 

54-2 

69.4 

5i' 

d 

14.93 

13-97 

13.3 

31-7 

40.8 

23' 

e 

14.15 

13-19 

12.9 

42 

e 

14.73 

13.77 

13.5 

42' 

e 

14.19 

13.24 

12.6 

29.8 

44 

e 

13.69 

12.73 

13.0 

28.8 

38.2 

16  THE   ROTATION    PERIOD    OF   THE    SUN    AS    DETERMINED 

TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No.  2442—  Confd. 

44' 

e 

14.41° 

I3.450 

13.5 

30.5 

46 

g 

14.15 

13.19 

13-0 

29.1 

39-0 

52.6 

49 

h 

14.64 

13-68 

14.2 

3L5 

40-7 

45 

j 

14.10 

13.14 

13.0 

30.4 

39-0 

45" 

I 

14.62 

13.67 

13-4 

No.  2452 

5/ 

d 

14.78 

13.83 

I7.I 

1893,  Aug.  5 

56' 

e 

13-93 

12.97 

16.5 

10^341x1 

54 

f 

14-57 

I3.6l 

17.3 

27.0 

40-3 

54-9 

58' 

g 

15-47 

14.51 

l8.5 

47" 

h 

13.29 

12.33 

15.6 

24.6 

62 

h 

14.66 

13.70 

I7.6 

26.8 

40.2 

55-8 

59 

j 

13.63 

12.67 

I7.I 

25.6 

38.3 

59' 

j 

I4.0O 

13.04 

17.4 

26.0 

No.  2465 

7i 

e 

14.58 

13.62 

9.8 

1893,  Aug.  6 

78' 

e 

14.71 

13-75 

9-8 

23.3 

5hIOm 

60 
61 

ff 

14.01 
14.14 

13.06 
I3.I8 

9-5 
9-3 

22.9 
22.3 

as 

48.0 

64' 

f 

13.97 

13.01 

9-3 

79 

f 

13.74 

12.78 

8.7 

21.7 

70 

g 

14.58 

13.63 

9.8 

77 

14.58 

13.62 

9-8 

62' 

13.65 

12.69 

9.1 

79' 

h 

14.11 

13.15 

9.1 

22.3 

So 

h 

14.17 

13.21 

9.1 

22.4 

63' 

j 

13.93 

12.97 

8-9 

22.0 

65 

j 

14.07 

13.11 

9.1 

22.2 

36.2 

69 

j 

13.40 

12.44 

8.7 

20.6 

34.5 

74 

j 

14.66 

13.70 

8.8 

22.3 

37.9 

6/ 

I 

14-39 

13.43 

8.5 

22.4 

37.0 

48.3 

64 

n 

14.26 

13.30 

9-5 

22.7 

36.7 

68 

jpr 

14.26 

I7.7Q 

22.8 

36.6 

No.  2471 

49' 

& 
h 

*.£J,»«rV/ 

14.74 

AO  •  Ov 

13.78 

13.6 

28.0 

1893,  Aug.  7 

50 

d 

15.08 

14.12 

13.5 

28.8 

I0h27m 

66' 

j 

14-43 

13.47 

13.7 

27.5 

80' 

j 

14.03 

13.07 

12.8 

75 

d 

14.03 

13.07 

13-0 

26.7 

78 

c 

14-33 

13.38 

12.9 

27-3 

83 

p 

13.97 

13.01 

12.6 

26.9 

^s.i 

64.1 

84 

Q 

e 

15.27 

14.31 

12.9 

*  -7 

28.0 

O*-**  J- 

42.4 

80" 

h 

13.56 

12.  60 

12.3 

69' 

j 

I4.I8 

13.22 

12.9 

No.  2482 

82 

c 

15.13 

14.17 

15.1 

1893,  Aug.  8 

77' 

g 

14.37 

13.41 

14.2 

26.6 

gh^m 

64" 

n 

13.91 

12.95 

13.8 

89 

K 

I3.8I 

12.85 

13.3 

25o 

00 

pr 

13.88 

I2.Q2 

n  8 

2^  4 

Cj  2 

V 

92 

f 

*O'"" 

14.67 

J"*'  •y*1 

13.71 

J.^}  .U 

13.7 

^.J  'T1 

27.2 

O  A  ••** 

04 

; 

14.12 

1^.16 

14  O 

2^  Q 

52.0 

J7*T 

Q5 

y 
; 

A*T  '  X 

14.08 

A  O  *  •*•  w 

IT..  12 

±L^.\J 
13.8 

•^o  *y 

2^  Q 

3**  •*•* 

51.8 

96 

j 

i 

14.33 

x  o  •  x 
13.37 

AO  •*-' 

14.0 

•*O  'V 

26.7 

O     * 

52.0 

97 

i 

13.91 

12.  95 

j.^|..vy 

17.7 

;:  ' 
26.0 

»}     *  :? 

78.6 

96' 

y 

/' 

14.42 

J- 

13.46 

*o*  / 

14.2 

26.2 

53.2 

j 

FROM    THE    MOTIONS    OF   THE    CALCIUM    FLOCCULI. 
TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


17 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

1 

2 

3 

4 

5 

6 

No.  2496 
1893,  Aug.  9 

I  lh26m 

98 
99 
106 

101 

a 

f 
a 
g 

I4.670 
14.67 
14.62 
I3.8l 

13-71° 

I3'S 

13.66 
12.8=5 

12.6 
12.6 

12.3 
1  1.  6 

38.4 

77    I 

67.7 

106' 
104 

c 
a 

14.40 
13.56 

13.44 
12.60 

12.3 
10.4 

36.3 

K>8' 

9i 
93 
97' 
83' 
90' 

g 
a 

f 
j 
i 
i 

13-55 
14.06 

13.65 
13.97 
13.65 
13.80 

12-59 
13.10 
12.69 
13.01 
12.69 
12.84 

12.6 
12.0 

11.6 
11.9 
ii.  6 

12.  0 

33-0 

77  n 

62.8 

90" 
103 

i 
f 

13.87 
13.97 

12.91 
13.01 

11.8 
11.9 

•JQ.O 

No.  2501 
1893,  Aug.  10 

102 

IO7 

j 
a 

14.00 
I3.8O 

13.04 
12.84 

24.8 

25.7. 

53-1 

9h23m 

87 

b 

14.66 

17.70 

27.0 

T08 

P 

I  -i  42 

0  '" 

12  46 

*•/•*; 

24  6 

No.  2521 

118 
118' 

109 

A 

t 

g 
(i 

13.62 
13.57 

14.  52 

12.66 

12.  6l 

17.  C^ 



24.2 
25-6 

28  5 



52.0 
5L3 



80.0 

1893,  Aug.  12 

no 

i 

I4.I8 

13.22 

28  I 

57  2 

8^47" 

III 

P 

14  40 

T7   44 

28  2 

112 

n  80 

12  QT, 

27  2 

III 

n  80 

12  QT. 

27  2 

114 

ft 

14  10 

17   14 

*/'~ 

27  6 

IIC 

i 

14.04 

1  3.  08 

89' 

i 

14.57 

1J.WO 
17.  OI 

28  7 

12?' 

i 

14.25 

1  7.  2O 

28  o 

102' 

j 

f~o 

M.6o 

17.72 

28  o 

108" 

g 

1C.  27 

14.71 

T.O.I 

No.  2542 

116 

f 

14.11 

13.15 

1891,  Aug.  14 

124 

y 

Mid 

it  18 

o  2 

^8  Q 

52  2 

65  Q 

Ijhcm 

133 

y 

14  31 

17    7C 

20  7 

40  I 

52  8 

132 

c 

13.70 

12  74 

28  I 

77  Q 

50  4 

63.1 

135 

i 

17.  QI 

12.  Q^ 

28  7 

38  7 

No.  2558 
1893,  Aug.  16 

4hoom 

129 

137 
138 

e 
i 

rf 

I4.IO 

14.57 

14  58 

13.14 
13.61 

17    62 

10.  1 
10.2 

10  6 

22.7 
24  0 

35.9 

77  Q 

66  9 

70  3 

No.  2560 
1893,  Aug.  17 

141 
139 
136 
140 
143 
150 
150' 
134 

142 

ICJ 

f 
i 
h 
i 

I 

h 
g 

f 
n 

14.40 
14.24 
14-37 
13.31 
14.21 
13.84 
14.54 
14.29 

14.63 
13  06 

13.44 
13.27 
13.41 

12.35 

13.25 
12.87 
13.57 
13.32 

13.66 

13  oo 

9-7 
9-9 

IO.O 

9-3 
9-9 

IO.O 

9-7 

IO.O 

13.5 

12  8 

22.8 
23.1 
23.3 
21.0 

22.4 
23-4 

26  o 

o/.y 
36.6 

34.1 

54  5 

62  6 

ioh38m 

152 

IC7 

I 
n 

13.10 
14  10 
1 

12.14 

17    14 

12.0 

ii  8 

26.0 

55.0 

18  THE   ROTATION    PERIOD    OF   THE   SUN    AS   DETERMINED 

TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No.  256o—Cont'd. 

157 

n 

14.96° 

14.00° 

I3-I 

27.6 

156 

h 

15.84 

14.87 

13.6 

29.3 

155 

h 

14.25 

13.29 

12.0 

26.2 

163 

f 

14.55 

I2.O 

28.9 

57.1 

60.0 

150" 

h 

**T*Oil 

13-23 

12.26 

x        '  y 

12.  1 

o/  •  •*• 

^-'y  •  y 

160' 

j 

13.94 

12.97 

12.8 

No.  2569 

145 

f 

12.78 

12.81 

12.5 

1893,  Aug.  18 

1  60 

j 

13.24 

13.28 

42.6 

164' 

j 

14  4 

45-0 

j 

14.64 

13^68 

14  5 

43-8 

C7    7 

1  68' 

d 

14.75 

151 

44  ^ 

o/  o 
C7  c 

140' 

i 

14.76 

13.80 

13-5 

HH*O 

o  /  *  o 

171 

I 

13.09 

I4.I 

41.8 

54.0 

» 
171' 

I 

15.30 

14.34 

14.0 

OH*  -7 

165' 

d 

14.52 

14.  1 

43.5 

No.  2580 

x  w,j 

AH*O 

' 

**!••  * 

HO  *O 

1893,  Aug.  19 

No.  2588 

194 

I 

14.48 

13.51 

13.0 

1893,  Aug.  21 

165 

d 

14.06 

13.10 

12.6 

3hI3m 

170 

n 

13.23 

12.26 

n.8 

174 

h 

15.11 

14.15 

13.6 

175 

h 

13.86 

12.90 

12.4 

176 

h 

14.15 

13.19 

12.7 

180 

j 

13-86 

12.90 

12.4 

181 

k 

13.55 

12.59 

12.  1 

183 

c 

13-55 

12.59 

12.  1 

184 

c 

15-45 

14.49 

13-9 

185 

e 

13.99 

13.02 

12-5 

186 

I 

13.60 

12.64 

12.2 

187 

j 

14.48 

13.51 

13-0 

188 
189 

j 
j 

13.55 
14.06 

12.59 
13.10 

12.  1 
12.6 

190 

j 

13.73 

12.77 

12.3 

191 

f 

14.36 

13.40 

12.9 

197 

m 

13.55 

12.59 

12.  1 

195 

k 

13.33 

12.36 

11.9 

196 

k 

13.46 

12.50 

12.0 

No.  2590 

1893,  Aug.  22 

2^25™ 

No.  2598 

199 

k 

13.36 

12.39 

15-0 

1893,  Aug.  28 

200 

k 

13.07 

12.  II 

I5-I 

24.1 

38.0 

lOh^Qm 

206 

i 

13.93 

12.96 

16.0 

25.9 

40.6 

208 

g 

14.40 

13.43 

16.2 

209 

m 

13.82 

12.85 

15.5 

211 

h 

14.40 

13-43 

16.2 

212 

h 

14.50 

13.53 

16.3 

213 

k 

13.49 

12.52 

15.1 

214 

i 

14.44 

13.47 

16.4 

26.9 

42.1 

215 

i 

14.25 

13.28 

16.3 

26.3 

41.7 

217 

b 

15-12 

14.15 

17.1 

2I9 

h 

14.21 

13.24 

16.2 

27.1 

FROM    THE    MOTIONS    OF   THE   CALCIUM    FLOCCULI. 
TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


19 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No.  2617 
1893,  Aug.  29 

4h03m 

220 
221 
222 
223 

k 
k 
k 
e 
i 
h 

13-37° 
13-09 
12.  80 
14-63 
14.23 
14  2$ 

12.40° 
12.12 
H.83 
13-66 
13.26 
13  28 

9.6 
9-7 

10.  1 

11.  7 
10.3 

II  0 

23-4 
22.8 
22.3 
25-8 
25.1 
24  7 

36  8 

40  4 

77  0 

No.  2619 
1893,  Aug.  30 

I2ho3m 

225 
228 
230 
231 

232 

237 

b 
d 
b 
i 
d 
f+h 

s 

13-88 
14.46 
12.37 
15.65 
14.72 
14.36 
14.72 
I4.I8 

12.91 

13.49 
11.40 
14.68 
13-75 
13-39 
13.75 
13.21 

13-6 
14.2 
12.5 
15.5 
14.6 

14.4 
14-5 
13.5 

22.1 

26.6 
26.0 
26.7 
25.8 

39.8 

65? 

238 

i 

14  10 

13.22 

14.3 

2^.0 

^ 

0^.2 

No.  2628 
1893,  Aug.  31 

lh28m 

240 
242 

233 

241 
239 

246 

8d 

e 

f 

/' 

14.87 
14.48 
14.82 

14.77 
14.74 
14.78 
14  dt 

13.90 
13.51 
13.85 

13.80 

13-77 
13-81 
13.46 

15-3 
13.7 
14.6 

12.2 
12.  1 

12.3 

II.  I 

27.0 
25.7 

25.0 

25.3 
23.9 

39-0 

"52.1 

247 
248 
249 
250 
251 

h 
f 

14.49 
14.96 
12.98 
13.96 
14.77 

13.52 
13.99 
12.01 
12.99 
13.36 

II.  I 
II.  0 

10.6 
14.8 
11.7 

24.5 
24.0 

23-8 

24.5 



50.4 
50.6 



75-9 

252 
2^3 

e 
g 

14.61 

14  i  e 

13.64 

13.  18 

12.0 
12.  1 

24.7 
24.7 

51.0 

254 

$ 

s, 

h 

13-73 
14.29 
13.84 

J.J.XW 

12.76 

13.32 
12.87 

II.  I 

II.  2 
9.7 

23.1 
24.2 
22.4 

49-7 

No.  2634 
1893,  Sept.  i 
ioh4im 

257 

258 

259 
260 
26l 
262 
263 
264 

% 

267 

h 
d 

d 

fd 

h 

i 

{ 

14.94 
14.87 
14.42 
I5.32 
15-03 
15.79 
15.32 
15.18 
14.06 

I5-7I 
14  DO 

13.97 
13.90 

13.45 
14.35 
14.06 
14.82 
14.35 

14.21 

13.09 
14.74 

n  72 

13.2 

I3-I 
12.7 

13-5 
13-3 
14.0 

13-5 
13.4 
12.4 

13.9 
1^  0 

40  O 

268 

g 

14  7Q 

13  82 

It  0 

41  2 

269 

27O 

; 
j 

13-86 
14  32 

12.89 

13.  3^ 

12.2 

13.2 

30.8 

No   2639 

271 

244' 

{ 

cr 

13-86 

13  68 

12.89 
12  71 

12.2 

2=;  8 

1893,  Sept.  2 

phjgm 

273 
275 
2?6 

s 

t 

h 

14.01 
13-66 

14  08 

13.04 
12.69 
13.  II 



26.0 

31 



52.5 

Si.J 

53.6 

68.2 

278 

1 

14.10 

13.22 

20.  Q 

20  THE   ROTATION    PERIOD    OF   THE   SUN    AS   DETERMINED 

TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No  2639  —  Con?  d 

27Q 

f 

14  S2° 

13  SS° 

27.=; 

*/y 

280 

i, 

14  08 

13  II 

as:i 

C4  4 

69.3 

281 

or 

13  72 

12  7^ 

2=5.7 

3^*7 
CQ  O 

"y-o 

6s.  s 

No  2651 

274 

; 

14  67 

13.70 

27.2 

1803   Scot  4 

283 

i 

14.42 

13.4^ 

27.0 

41.6 

IO^I2m 

* 

^7 
13.03 

12.66 

'   ;: 

2=;.  6 

30.2 

288 

m 

14.  S7 

13.  60 

-^j.w 
26.0 

200 

h 

14.  q8 

J.J.V./W 

13.61 

27.0 

201 

?, 

M.C7 

XO.V/i 

I3.6O 

' 
26.0 

2Q2 

f, 

14.  S8 

J.J.V./W 

13.61 

27.0 

203 

I 

14.98 

14.01 

27.8 

204 

\ 

14.73 

J.tf.Vi 

13.76 

27.3 

207 

f 

14.69 

13.72 

27.9 

42.4 

208 

Jf 

13  01 

28  o 

43  O 

301 

J 

or 

14  38 

13  41 

27  0 

42  7 

qe  Q 

302 

£ 

fl 

14  S7 

13  60 

'' 
2O  0 

3O4 

d+f 

Aif.O/ 

13  62 

i^).W 

12  6^ 

27.7 

30  I 

305 

f 

14.42 

1^  4C 

27.4 

oy.i 

41  O 

306 

or 

14.13 

1^.16 

2=5.7 

40  7 

No.  2675 
1893,  Sept.  6 

9h47m 

No.  2681 

310 
311 
314 
315 
3l6 
319 

320 

326 
289 

h 

{ 

b 

d 
g 

Sf 

g 

14.02 

13.84 
14.41 
15.84 
14.12 
14.67 
15-21 
13-74 

14.12 

13.05 
12.87 
13-44 
14.87 
13-15 
13.70 
14.24 
12.77 

13.  11? 

14.4 
14.2 
14.8 
16.4 
14.5 
I5-I 
15.7 
I4.I 

ic.-z 

^3.0 

1803,  Sept.  7 

320 

h 

14.00 

13.12 

14.0 

C2.Q 

I2hjgm 

330 
331 

{ 

**fwJj 

15.26 
14.04 

14.29 
13.07 

15.4 

IS.  I 

=52.7 

332 
333 
334 

$ 
III 

330 

i 

k 
k 

i 
i 
g 

or 

14.64 
14.92 
14-07 
13.14 
14.07 
13.56 
14.34 
14.28 

*O-"/ 

13.67 

13-95 
13.10 
12.17 
13-10 
12.59 

13.37 
13  31 

14.7 
15.0 
I4.I 

I3.I 
I4.I 

13.5 
14.4 
14  6 

^3.7 

No.  2694 

340 

744 

* 

I 

e 

12.94 
14.06 

11.97 
13.00 

12.9 

38  5 

1893,  Sept.  8 

34  c 

h 

13.66  ' 

xo-"y 
12.  60 

VJ  ^ 

2hI2m 

346 

h 

XJ.VW 

14.06 

13.00 

38  s 

347 

d 

*tpv~ 

14.06 

13.00 

38  =5 

No.  2699 

3S3 

f 

14.26 

13.20 

40  I 

^2.2 

1893,  Sept.  ii 

354 

f 

14.61 

i^.^y 
I3.O4 

40.3 

I2h48m 

355 

f 

14.52 

17.  CC 

40  0 

356 

d 

15.19 

M.22 
~ 

42  o 

357 

d 

14.13 

I3.l6 

38.8 

S3.  2 

358 

d 

14.16 

13.10 

38.5 

S3.  1 

360 

f 

14.44 

13.47 

30.8 

FROM    THE    MOTIONS    OF   THE    CALCIUM    FLOCCULI. 


21 


TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

i 

2 

3 

4 

5 

6 

No.  2712 

361 

b 

14.30° 

13.32° 

13.9 

1893,  Sept.  14 

362 

d 

14.30 

13.32 

13.9 

363 

d 

14.20 

13-22 

13-8 

364 

d 

14.39 

13.41 

14.0 

365 

d 

13.69 

12.71 

13.3 

% 

ff 

14.39 
13.15 

13.41 
12.17 

14.0 
12.7 

372 

f 

14-77 

13.79 

14.4 

373 

f 

15.17 

14.19 

14.8 

374 

f. 

14.67 

13.69 

14.3 

375 

i 

I3.8I 

12.83 

13.4 

376 

i 

14.59 

I3.6l 

14.2 

377 

i 

14.59 

I3.6l 

14.2 

380 

g 

13.15 

12.17 

12.7 

c 

15.84 

14.86 

15-5 

382 

c 

14.30 

13.32 

13.9 

383 

i 

14.67 

13.69 

14.3 

i 

I3.8I 

12.83 

13.4 

386 

c 

13.69 

12.71 

13.3 

387 

d 

13.52 

12.54 

13.1 

388 

I 

H.53 

10.55 

II.O 

389 

i 

13.90 

12.92 

13.5 

39i 

h 

13.42 

12.44 

13-0 

392 
393 

i 

12.53 
13.24 

11.55 
12.26 

12.  1 
12.8 

394 

d 

13.69 

12.71 

13.3 

No.  2722 

1893,  Sept.  15 

No.  2741 

405 

e 

14.89 

13.91 

14.3 

1893,  Sept.  22 

406 

e 

14.98 

14.00 

14.4 

nhi3m 

407 

c 

14.98 

14.00 

14.4 

410 

a 

14.34 

13-36 

13.7 

411 

a 

14.79 

13.81 

14.2 

412 

e 

15.28 

14.30 

14.7 

414 

e 

14.70 

13.72 

I4.I 

415 

c 

I4.6O 

13.62 

14.0 

417 

d 

14.44 

13.46 

13-8 

418 

d 

15.08 

14.10 

14-5 

420 

f 

14.60 

13.62 

14-0 

422 

c 

14.79 

13.81 

14-2 

429 

e 

14.51 

13-53 

13.9 

428 

e 

15.38 

14.40 

14.8 

No.  2756 

1893,  Sept.  23 

nh53m 

No    2777 

447 

14.07 

13.08 

Mo 

7 

-LTV-f.     ^»/  /  / 

1893,  Oct.  4 

448 

c 

14.22 

13-23 

•*w 

13.8 

' 

9"  1  6m 

450 

c 

14.42 

13.43 

14.0 

45i 

c 

14.78 

13.79 

14.4 

452 

c 

14.42 

13-43 

14.0 

455 

a 

15.05 
14.76 

14.06 

14.7 

!3>9 

42.2 

457 

d 

13.54 

12.55 

13.1 

T^       * 

22  THE   ROTATION    PERIOD    OF    THE   SUN    AS   DETERMINED 

TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 

synodic. 

I 

2 

3 

4 

5 

6 

No.  2777  —  Cont  'd. 

4=;8 

b 

I4.090 

13.10° 

17.7 

70.0 

*fow 

d 

14.03 

XO  •  / 
17.4 

OV  my 

7,0.  0 

461 

d 

14.31 

13.32 

*«J  *tt 

13.9 

Oy  *?r 

462 

j 

14.47 

17.44 

17.7 

41.1 

^ 

463 

J 

i 

-L*-r**-rO 

14.22 

XO  •T'T1 
13.23 

xo  •  / 

13.8 

464 

n 

13.81 

12.82 

13.4 

465 

I 

13-81 

12.82 

13.4 

466 

n 

12.76 

11.77 

12.3 

467 

f 

14.13 

13.7 

468 

d+f 

13.81 

12.82 

13.4 

469 

d 

13.54 

12.55 

13.1 

471 

I 

14.09 

13.10 

13.6 

472 

a 

14.31 

13-32 

13.9 

473 

h 

14.67 

13-68 

14.3 

474 

f 

14-13 

I3.I4 

13.7 

No.  2787 

470 

a 

14.00 

27  0 

A1  W  •      **  J\J  J 

1893,  Oct.  5 

*T/  w 

477 

a 

•*-*T  '  Vw 

14.48 

I3.49 

*/  *y 

27  0 

I0h22m 

TV  / 

*fcf  *tfW 

•*/  •** 

No.  2791 

481 

h 

14  ^6 

i 

26.1 

39.8 

1893,  Oct.  7 

AjAJJi 

482 

h 

14^4 

j  -j  c  e 

I0h26m 

L^\J^ 

483 

f 

13.97 

12.98 



25-7 

39-7 



65.5 

484 

f 

13.87 

12.88 



25-3 

39-0 



65.3 

48; 

f 

13.84 

12  8c. 

"7O   ? 

55-6 

T"°O 

486 

f 

14.27 

J.A  .U  J 

T7.   28 

2^*2 

^06 

ij.<_nj 
487 

d 

1  o  «^(J 

25^8 

*!**/ 

488 

d 

14^2 

J«'eo 

39.8 

480 

b 

14^2 

T7    C2 

2^7 

40.2 

t'-'y 

h 

T4^7 

I?^8 

26.0 

4O.  I 

4OI 

a 

14.46 

1^47 

2C   7 

40.7 

4Q2 

y 

14.  co 

J-3    60 

^3  *»J 

*TV'SO 

ty 
40  c 

o. 

•^T"  '  O.7 
14.10 

iO'^~nJ 
13.11 

2C   A 

38.2 

No.  2797 

T".7O 

493 

g 

14.68 

13.69 

14.4 

O*"7"  ** 

1893,  Oct.  9 

494 

g 

14.68 

13.69 

14.4 

8hI0m 

497 

g 

14.46 

13.47 

14.2 

498 

I 

13.89 

12.90 

13.6 

499 

e 

13.54 

12-55 

13.2 

500 

f 

14.43 

13-44 

14.3 

31.6 

42.0 

501 

f 

14.63 

13.64 

16.0 

33-2 

42.8 

502 

j 

14.35 

13.36 

14.1 

503 

j 

14-55 

13.56 

14.3 

504 

I 

15.34 

14-35 

15.1 

505 

f 

15.34 

14.35 

15.1 

506 

g 

13.72 

12.73 

13.4 

507 

a 

14.20 

13.21 

13.9 

508 

I 

14.02 

13.03 

13.7 

No.  2800 
1893,  Oct.  10 

509 

g 
Sf 

13.56 
13.65 

12.57 
12.66 

15.2 
15.4 

25.0 

25-3 

9028*° 

512 

f 

14.50 

13.51 

17.2 

27.0 

513 

h 

13.85 

12.86 

16.8 

25-7 

514 

d 

14.50 

13-51 

16.9 

27.0 

515 

f 

14.39 

13.40 

16.9 

26.8 

f 

13.80 

12.  8l 

16.9 

25.6 

FROM    THE   MOTIONS   OF   THE   CALCIUM    FLOCCULI. 
TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


23 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

i 

2 

3 

4 

6 

No.  28oo—Cont'd. 

517^ 

m 

I3.400 

I2.4I0 

14.1 

24.8 

k 

12-75 

11.76 

15.2 

522 

d 

15.10 

14.11 

18.6 

28.2 

525 

h 

14.14 

13.15 

17.2 

26.3 

No.  2809 

519 

f 

14.09 

13.10 

9-5 

1893,  Oct.  ii 

520 

d 

14.24 

13.25 

9.6 

^ho^rn 

523 

f 

12.99 

12.00 

8.7 

524 

f 

13.98 

12.99 

9.4 

528 

h 

14.09 

13.10 

9.5 

529 

h 

13.67 

12.68 

9.2 

No.  2812 

1893,   Oct.   12 

9h26m 

No.  2818 

530 

d 

14.87 

13.88 

14-3 

27-5 

1893,  Oct.  16 

531 

d 

14.60 

13.61 

14.2 

27.0 

ioh30m 

532 

k 

14.27 

13-28 

13.9 

26.4 

39-3 

533 
534 

{ 

14.05 
14.39 

13.06 
13.40 

14.0 
13-9 

2$ 

f 

14.70 

13.71 

14.2 

536 

j 

14-39 

13.40 

13-9 

537 

I 

14.30 

13.31 

14.3 

26.4 

538 

I 

14.10 

13-11 

13.6 

539 

k 

14.10 

13.11 

13.6 

26.4 

38.8 

541 

i 

13.71 

12.72 

13.2 

24.9 

37-6 

543 

j 

14-39 

13.40 

13.7 

26.6 

544 

I 

13.98 

12.99 

13.4 

25.8 

545 

I 

14.79 

13.80 

14.6 

27.4 

546 

I 

13.29 

12.30 

12.6 

24.4 

548 

e 

15.27 

14.28 

14.8 

549 

i 

14.35 

13.36 

14.1 

26.8 

39.6 

550 

k 

13-73 

12.74 

13.2 

552 

c 

15.01 

14.02 

14.9 

27.8 

553 

a 

14.99 

14.00 

14-5 

554 

a 

15.48 

14.49 

15-0 

556 

h 

14.34 

13.35 

14.8 

27.0 

40.0 

No.  2821 

540 

i 

13.91 

12.92 

12.5 

24.8 

1893,  Oct.  17 

542 

k 

I3.8I 

12.82 

12.9 

24.6 

iih25m 

559 

e 

15.29 

14.30 

13.5 

s6o 

£ 

14  60 

13.61 

12  8 

26.2 

^  ^  A. 

5uu 
56l 

h 

13^86 

12^87 

I2.S 

24.7 

' 

h 

14.62 

13.63 
12.56 

12.8 
13.2 

26.3 

52.1 

1 

567 

g 
g 
e 

14.27 
13-95 
13-56 

13.28 
12.96 
12.57 

12.5 

12.2 
12.0 

24.1 

o**  •  * 

568 

f 

13.42 

12.6 

26.3 

55.0 

Ovn-7 

ff 

14.01 

1  3.02 

•^^•O 

25.6 

000 

j 

•** 

No.  2829 

569 

m 

13-43 

12.44 

12.  1 

1893,  Oct.  18 

C7Q 

or 

12.94 

12.5 

4i.3 

ioh03m 

OX" 
571 

& 
C 

13.97 

12.98 

13.6 

T"1-  *O 

572 

C 

14.34 

13-35 

13.0 

24:  THE   ROTATION    PERIOD    OF   THE    SUN    AS   DETERMINED 

TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

5 

5 

6 

No.  2829  -Cont'd. 

573 

h 

14.88° 

I3.890 

13-5 

C*7A 

•f 

T  A.  OQ 

I3.IO 

12.5 

41.9 

575 

k 

13.24 

12.25 

II.Q 

No.  2831 

C77 

c 

14  24 

13  25 

20  3 

1893,  Oct.  io 

O/f 

14  24 

13  25 

29.3 

*v'5ri.lJ     x-rvrv«     x.y 

cgj 

e 

14  24 

T^"2e 

20.3 

582 

i 

JC.7Q 

14.  80 

•  y  o 

32.7 

No.  2839 

o^** 

•*•*?*/;/ 

&*f  «WVf 

O^**  / 

1893,   Oct.  21 

No.  2870 

583 

h 

13.31 

12.31 

12.5 

1893,  Nov.  6 

584 

h 

14.51 

13.51 

13.7 

ioh5im 

585 

/ 

15.70 

14.70 

14.9 

C&fS 

/ 

14.01 

13  OO 

17.  C 

39-0 

587 

Jf 

14.08 

AO  ***** 

13  07 

•*•  o  *  o 

13.8 

39«i 

5887 

j 
a 

13.84 

•LO'<-'/ 

12.84 

*O  •<tj 

13.0 

589 

f 

15.39 

14.39 

14.6 

590 

h 

14.33 

13.33 

13.5 

CQT 

j 

14.56 

17.  CC 

13.6 

40.9 

CQ2 

Jf 

AO  •  OO 

13.44 

XO  •  v^ 
17.  C 

40.4 

ov 
594 

h 

13-93 

XO  •triT 

12.93 

•*-O*  O 

13.1 

596 

f 

14.80 

13.80 

14.1 

No.  2877 

597 

j 

14  IS 

13  14 

26.1 

1893,  Nov.  7 

598 

J 
j 

14  \0 

13.40 

26.8 

nhi4m 

j^^ 
607 

J 

h 

14.50 

xo  .^y 
13.49 

26.8 

608 

a 

13.69 

27.2 

No.  2880 

603 

h 

I4.6l 

13.60 

14.0 

1893,  Nov.  9 

604 

j 

13.13 

12.12 

12.5 

ioh53m 

605 

j 

12.36 

H.35 

11.7 

606 

J 

14.40 

13-39 

13.8 

610 

n 

14.29 

13-28 

13.7 

611 

h 

14.10 

13.09 

13-5 

No.  2888 

1893,  Nov.  io 

nh35m 

No.  2898 

612 

i 

14.56 

13.55 

13-4 

1893,  Nov.  17 

613 

g 

13.96 

12.95 

12.8 

IIh26m 

614 

g 

14.27 

13.26 

13.1 

615 

d 

14.56 

13.55 

13.4 

616 

I 

13.56 

12.55 

12.4 

617 

I 

13.56 

12-55 

12.4 

621 

i 

14.77 

13.76 

13.6 

622 

P 

12.13 

II.  12 

II.  0 

626 

n 

12.84 

H.83 

ii.  7 

631 

d 

14.06 

13.05 

12.9 

No.  2904 

1893,  Nov.  18 

IIhI2m 

FROM    THE    MOTIONS    OF    THE    CALCIUM    FLOCCULI. 
TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


25 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No.  3020 

632 

f 

14.19° 

13.17° 

12.7 

i894>hJarK  25 

633 

f 

14.09 

13.07 

12.6 

634 

d 

13.98 

12.96 

12.5 

635 

d 

13.89 

12.87 

12.4 

636 

14.09 

13.07 

12.6 

637 

13.79 

12.77 

12.3 

639 

f 

14.19 

13.17 

12.7 

640 

f 

14.40 

13.38 

12.9 

641 

e 

13-57 

12.55 

12.  1 

642 

g 

14.09 

13.07 

12.6 

644 

d 

13.69 

12.67 

12.2 

648 

j 

14.51 

13.49 

13-0 

650 

f 

13.79 

12.77 

12.3 

651 

I 

13.79 

12.77 

12.3 

652 
653 

I 
n 

13-57 
13.98 

12.55 
12.96 

12.  1 

12.5 

No.  3028 

1894,  Jan.  26 

IIh32m 

No.  3062 

654 

f 

14.70 

13.70 

13.7 

1894,  Feb.  27 

h 

14.30 

13.30 

13.3 

ih33m 

656 

j 

14.40 

13.40 

13.4 

657 

j 

14.00 

13.90 

13.9 

658 

h 

14.50 

13.50 

13.5 

659 

I 

13.80 

12.80 

12.8 

660 

I 

14.30 

13.30 

13.3 

661 

j 

I4.0O 

13.00 

13.0 

662 

j 

14.30 

13.30 

13.3 

663 

j 

13.90 

12.90 

12.9 

664 

J 

14.30 

13.30 

13.3 

665 

j 

13.90 

12.90 

12.9 

666 

j 

13.90 

12.90 

12.9 

667 

j 

14.40 

13.40 

13.4 

668 

h 

14.80 

13.80 

13.8 

669 

f 

14.80 

13-80 

13.8 

670 

c 

14.70 

13.70 

13.7 

671 

a 

13.80 

12.80 

12.8 

672 

b 

14.80 

13-80 

13.8 

673 

b 

13.80 

12.80 

12.8 

674 

a 

14.70 

13.70 

13.7 

675 

e 

13.70 

12.70 

12.7 

676 

i 

15.10 

14.10 

14.1 

677 

d 

15.00 

14.00 

14.0 

678 

f 

14.80 

13-80 

13.8 

No.  3069 

679 

h 

14.71 

I?  71 

28.4 

40.3 

1894,  Feb.  28 

680 

h 

AT"*  /   X 

xo  •  /  -*• 

68  1 

h 

iTcU 

12.93 

26!? 

38.4 

682 

f 

14.22 

13.22 

AVS«  J 

27.^ 

38.8 

683 

j 

"'i  '  O 

27.0 

38.8 

684 

h 

ic.  14 

14  14 

/  *w 

29.2 

68=; 

x  O  *  ^-T1 
14.35 

13.35 

27.  C, 

v-"-7D 

686 

nt 

13.00 

12.88 

*•  /   •  J 

687 

k 

27.7 

\j\j  / 

1 

26  THE   ROTATION    PERIOD    OF    THE    SUN    AS   DETERMINED 

TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No.  3079 
1894,  Mar.  2 

3*1  10m 

No.  3082 
1894,  Mar.  3 

I2hIOm 
No     3003 

689 
690 
69I 
692 

693 
694 

1 

609 

h 
f 
j 
j 
C 

e 
e 
i 
i 
k 

e 

I5.290 
15.06 
14.71 
14.37 
14.37 
14.03 
14.60 
14.14 
14.26 
14.03 

14  54 

I4.290 
I4.O6 
I3.7I 
13.37 
13-37 
13.03 
13.60 

13.14 
13.26 

13.03 

1^,  54 

12.5 
12.3 
12.0 

ii.  7 
ii.  7 
11.4 
11.9 

"•! 

ii.  6 
11.4 

28.4 

1894   Mar   8 

700 

a 

14  ^5 

17    7,5 

28.O 

Tih^em 

7O2 

f 

14.64 

17    64 

28.6 

70^ 

f 

14.40 

17    4O 

28.1 

7O4 

f 

14.40 

I7.4Q 

28.3 

70  ^ 

f 

14.40 

I7.4Q 

28.3 

706 

1 

14.35 

13.35 

28.0 

707 

Jf 

n.88 

700 

f 

14.49 

I7.4Q 

2o  ., 

710 

y 

M.4Q 

I7.4Q 

083 

711 

/ 

I4.^O 

17.70 

27.0 

712 

/ 

**I"OV' 

14  60 

«•>•-> 

I  7.  60 

28.7 

71^ 

y 

i^.uy 
I4.O4 

1^.64 

28.6 

714 

/ 

14.7.5 

17.7,5 

28.0 

71  c 

\ 

I4.7Q 

17.70 

27.0 

716 

h 

14.7!; 

17.7,5 

28.0 

717 

i 

14.40 

13.40 

28.1 

718 

i 

14.68 

13.68 

28.7 

719 

h 

14.40 

I  7.  4O 

VT 

68.8 

No.  3101 
1894,  Mar.  10 

2^04m 

No.  3104 
1894,  Mar.  13 

2hI2m 

No.  3106 
1894,  Mar.  14 
ih59m 

721 
722 

723 
724 

725 
726 
727 
728 
729 
730 
733 
736 
74i 

731 
732 
734 
737 
738 

C 
C 

S 

e 
e 
c 
e 
S 
g 

b  +  d 

gf 

a 
b 
h 
e 
e 

12.91 

13.51 
14.22 
13.92 
14.02 
14.49 
14.42 
13.92 
13.31 
13.89 
14.62 
14.32 
14.02 

15.06 
14.24 

14.13 
14.20 
13.51 

11.91 
12.51 
13.22 
12.92 
13.02 
13.49 
13.42 
12.92 
12.31 
12.89 
13.62 
13.32 
13.02 

14.06 
13.24 

13.13 
13.20 
12.51 

11.8 
12.4 
13.1 

12.8 

12.9 
134 
13.3 

12.8 
12.2 
12.8 
13.5 
13-2 

12.9 

13.6 

13-6 
12.7 
12.7 

12.  1 

25.6 
26.4 

25-7 

26.9 
26.2 

39-6 
38.8 

38.7 

5i.i 

FROM    THE    MOTIONS    OF   THE    CALCIUM    FLOCCULI. 
TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

i 

2 

3 

4 

5 

6 

No.  3io6—Cont'd. 

739 

e 

14.23° 

I3.230 

12.8 

740 

c 

14.50 

13.50 

13.2 

27.4 

743 

a 

14.95 

13-95 

13.5 

748 

d 

14.98 

13.98 

13.1 

28.0 

40.8 

No.  3112 

744 

d 

14.87 

13.88 

14.7 

27.1 

1894,  Mar.  15 

IhI2m 

746 

d 
d 

14.20 
15-12 

13-21 
14.13 

13.8 
15.4 

25-8 
27.6 

747 

f 

15.17 

I4.I8 

15.4 

27.7 

749 

b 

14.71 

13.72 

14.6 

No.  3117 

750 

d 

15.39 

14.40 

12.8 

1894,  Mar.  16 

751 

b 

14.60 

I3.6l 

12.  1 

2h44m 

752 

h 

I3.8I 

12.82 

11.4 

753 

h 

14.38 

13-39 

11.9 

754 

{ 

15.39 
14.60 

14.40 
I3.6l 

12.8 
12.  1 

756 

i 

14.72 

13-73 

12.2 

757 

i 

14.60 

I3.6l 

12.  1 

758 

c 

13.25 

12.26 

10.9 

759 

g 

14.60 

I3.6l 

12.  1 

760 

c 

14.15 

I3.l6 

ii.  7 

No.  3121 

1894,  Mar.  17 

I2h04m 

No.  3185 

76! 

a 

14.30 

13-34 

13.7 

1894,  May  30 

762 

c 

14.98 

I4.O2 

14.4 

3hi6m 

763 

i 

14.59 

13.63 

14.0 

764 

e 

14.98 

14.02 

14.4 

765 

e 

14.20 

13.24 

13.6 

766 

g 

14.78 

13.82 

14.2 

767 

e 

14.20 

13.24 

13.6 

768 

c 

14.30 

13.34 

13.7 

769 

f 

14.49 

13.53 

13.9 

770 

I 

13.60 

12.64 

14.2 

24.2 

771 

f 

14.69 

13.73 

14.1 

773 

d 

14.49 

13-53 

13-9 

774 

f 

14.48 

13.52 

14.7 

25.9 

775 

f 

13.96 

13.00 

14.2 

24.9 

776 

c 

14.10 

13.14 

13.5 

777 

i 

13.38 

12.42 

14.0 

23-8 

778 

g 

1440 

13.44 

13-8 

779 

c 

14.59 

13.63 

14.0 

780 

e 

14.49 

13-53 

13.9 

No.  3190 

1894,  May  31 

3h55m 

No.  3191 

781 

g 

14.41 

1^.4=5 

24.8 

rt 

1894,  June  2 

/  w  A 

782 

T^'T 
I4.2O 

A  O  *T-  D 

T^ 

24  ^ 

/u^. 

783 

I^\4 

*""T-  •  O 

24.6 

/*-*O 

784 

MC7 

IT.    C7 

40.6 

53-8 

785 

a 

•  oo 
14.  -34 

•*•  O  •  O  / 

i  

23.7 

T^  * 

39>2 

53.1 

786 

g 

H^'OH 

14.52 

iV^6 

2=5.0 

787 

P 

14.  ?o 

' 

1 

/: 

24  6 

/*"*/ 

& 

°' 

28  THE   ROTATION    PERIOD    OF   THE   SUN    AS    DETERMINED 

TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

^[o.  3101  Cofit'd, 

788 

CF 

14  41° 

13  4^° 

24  8 

/uu 

& 

Aif.ifi 

A0«4O 

A£^«U 

780 

0- 

1^6^ 

12.69 

27  4 

/<jy 

7QO 

<5 
g 

AO  **~3 

13    87 

12  QI 

*O**I 

23  8 

/y" 

70  1 

I 

*o  *   / 

Id  CH 

A  ^/.v/o- 
13  07 

••^O  "*J 

24  I 

No.  3196 

/y-1 
792 

d 

•LLT*^JO 

14-57 

±  o  •  w/ 
I3.6I 

15-9 

A£}«  X 

28.9 

1894,  June  4 

793 

b 

15-13 

14.17 

15.6 

30.1 

9h25m 

794 

g 

13-93 

12.97 

14.8 

795 

d 

14.27 

13.31 

15.3 

28.3 

No.  3201 

797 

g 

14.31 

13.35 

I3.I 

1894,  June  5 

e 

14.21 

13.25 

13.0 

I2h53m 

800 

m 

13.60 

12.64 

12.4 

801 

0 

13.29 

12-33 

12.  1 

802 

m 

13.60 

12.64 

12.4 

803 

i  +  k 

14.21 

13.25 

13-0 

804 

j 

14.00 

13.04 

12.8 

805 

d 

14.21 

13.25 

13.0 

806 

i 

14.11 

13.15 

12.9 

807 

e 

14-51 

13.55 

13.3 

808 

g 

13-60 

12.64 

12.4 

809 

g 

13.19 

12.23 

12.0 

810 

g 

14.11 

13.15 

12.9 

No.  3204 

1894,  June  6 

I2h26m 

No.  3207 

813 

/ 

14.92 

13.96 

14.9 

1894,  June  ii 

815 

/ 

13.61 

12.65 

13-5 

I2h58m 

816 
817 

I 

14-54 
14.36 

13.58 
13.40 

14.5 
14.3 

818 

f 

15.01 

14.05 

15.0 

819 

f 

14-45 

13.49 

I4.I 

27.6 

819' 

a 

14.64 

13.68 

14.6 

820 

a 

14.92 

13.96 

14.9 

821 

a 

14-35 

13.39 

14-3 

27.4 

822 

c 

14.64 

13.68 

14.6 

823 

c 

14:82 

13.86 

14.8 

824 

e 

14.45 

13.49 

14.4 

825 

c 

14.36 

13.40 

14-3 

826 

c 

14.45 

13-49 

14.4 

827 

a 

14-59 

13.63 

14.7 

27-9 

828 

b 

14.73 

13.77 

14.7 

829 

d 

15.11 

14.15 

I5.I 

830 

/ 

14.35 

13.39 

14.5 

27.4 

831 

h 

14.35 

13-39 

14.2 

27.4 

832 

f 

14.87 

13.91 

14.8 

28.5 

833 

f 

14.36 

13  41 

14  2 

27  2 

53  6 

68.2 

« 

834 

h 

j.<+.jv 
14.36 

±  O  •*T-L 
13.40 

±*f  «^ 

14.3 

*/  .^ 

JO'^ 

835 
836 

h 

i 

14.64 

I4.4=» 

13-68 

1^  CQ 

14.6 
14  ^ 

27  ^ 

C-2    2 

837 

h 

T"T"O 

14.  57 

XO  •  O^7 

13.62 

±Lt  *O 

I  c  2 

*/  o 

27  Q 

OO"^ 
t'j  7 

838 

h 

•"•T-*  J  / 

14.30 

J.  ^  .  \J^ 

13.44 

*•  O' 

14  0 

/  *y 

27  6 

oo*/ 

C'Z    Q 

69.2 

*-'Ov-' 

839 

f 

A^'O;7 

14-43 

"-  O  •*-f*T 

13.47 

A£|.»vr 

14.2 

*'/  BVJ 

27.6 

oo  *y 

vyV 

840 

f 

14.65 

13.69 

14.3 

28.0 

840' 

f 

15.01 

14.05 

15.0 

FROM    THE    MOTIONS    OF   THE    CALCIUM    FLOCCULI. 


29 


TABLE  i.    Diurnal  Motions  of  the  Flocculi — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No.  3207—Cont'd. 
No.  3211 

844 
847 
822' 

841 

/ 

; 

c 

d 

14.86° 
14.64 
14.73 

14.82 

13-90° 
13-68 
13-77 

13.87 

I5i 
14.6 

14.7 
13.8 

28.5 

30.8 

1894,  June  12 

842 

a 

15.00 

14.  OS 

X0.w 

13.6 

7,0.7 

56.2 

2h?c,m 

83 

c 

14  70 

J-2    7C 

J-3.7 

•3Q    I 

ire   T 

Ir**3 

845 
846 
848 
840 

1 

14.32 

14-73 
14.42 
14  S7 

13.36 

13.77 

13.46 

13  62 

13.1 

13.5 
13.2 

J7.  C 

7Q    7 

No   3214 

gen 

b 

jc  -74 

14  30 

27  2 

1804    Tune  it 

8m 

f 

14.48 

13.  C7 

2C  Q 

41.8 

2h  07111 

"o1 
8=12 

y 

14  cj 

I3.C.6 

25.4 

41.0 

^ 

SCT. 

a 

14.  7C 

13.80 

J  7 
25.6 

41.8 

8cc 

h 

14  27 

1-5-32 

2^  O 

40  4 

8t;6 

i 

14  17 

I?  22 

2^  0 

40  0 

No.  3216 
1894,  June  15 

Ilh28tn 

857 
858 

859 
860 
861 
862 
863 

I 
j 

Jf 

C 

C 
g 

14.52 

14-34 
14.70 
14-87 
14.52 

I5-I4 
14.56 

13-57 
13.39 
13.75 
13.92 
13-57 
14.19 

13.61 

15.4 
15.2 

15-6 
15.8 
15.4 

16.1 

14.3 

47.6 

864 
865 
866 
867 
868 
869 
870 

h 

i 

h 
f 

e 

h 

15.23 
I4-I7 
15.05 
15.14 
14-87 
14.26 
14  77 

14.28 
13.22 
14.10 
14.19 
13.92 
13.31 

I  3  4^ 

16.2 
15.0 
16.0 
16.1 
15-8 
15.1 

14  Q 

40  2 

C7   0 

No.  3218 

871 
872 

877 

e 

c 

c 

L4'6/ 
I4.6l 

13-99 
14.17 

Lo-46 
13.66 
13.04 

1^  22 

15-5 
14-8 

27.2 

37.1 

1894,  June  16 

~/«j 

874 

e 

14.  -JQ 

1-3    ^C 

28.4 

77.7 

53-4 

63  7 

2h42m 

87=5 

f 

13.87 

12  02 

28.0 

s 
36.5 

51.4 

876 

d 

14.15 

I  7.  2O 

27.1 

37.1 

8^ 

d 

M4Q 

T  7   C4 

26.8 

38.3 

No.  3221 
1894,  June  1  8 
4h45m 

878 
879 
880 
881 
882 
883 
884 

886 
887 
888 
889 
891 
892 
893 

d 
b 
b 
b 
b 
d 

\ 

J 
3 
c 

ff 

13.80 
15.20 
14.64 
14.50 
14.78 
15.20 
14.92 
14.08 
15.06 
14.65 
14.50 
14.22 
14.28 
13.80 
14-43 

12.85 
14.25 
13.69 
13-55 
13.83 
14.25 

13.97 
13.13 
14.11 
13.70 
13-55 
13.27 

13-33 
12.85 
13.48 

9.2 

10.2 

9.8 
9-7 
9-9 

10.2 
10.  0 

9-4 

10.  1 

9-7 
9-7 
9.5 
9-5 

9i 

9.6 

25.9 

25-2 
25-5 

30  THE   ROTATION    PERIOD    OF   THE    SUN    AS    DETERMINED 

TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No.  3223 

890 

h 

I4.400 

13.45° 

15.7 

26.4 

40-5 

54-4 

1894,  June  19 

894 

d 

14.43 

13.48 

16.2 

26.5 

9h56m 

895 

e 

14.58 

13.63 

16.0 

No.  3228 

896 

d 

14.54 

13-59 

10.8 

24.9 

1894,  June  20 

897 

b 

14.92 

13.97 

10.7 

25.6 

2ho7m 

898 

a 

14.59 

13.64 

10.9 

25.0 

899 

a 

14.21 

13.26 

10.3 

24.3 

900 

g+i 

14.01 

I4.O6 

ii.  i 

901 

e 

14.25 

13.30 

10.5 

902 
903 

e 
c 

14.25 
14.76 

13.30 
I3.8I 

10.5 
10.6 

25.3 

904 

c 

14-44 

13.49 

10.  1 

24-5 

38.6 

905 

g 

14.75 

13.80 

10.9 

906 

g 

15.26 

14.31 

II-3 

908 

i 

I3.6l 

12.66 

10.  0 

909 

k 

13.69 

12.74 

10.  0 

23-1 

36.6 

912 

c 

14.47 

13.52 

IO.2 

24.7 

38.6 

913 

g 

13.74 

12.79 

10.  1 

915 

e 

13-99 

13.04 

10.3 

916 

e 

14.75 

13-80 

10.9 

917 

f 

14.88 

13.93 

II.  0 

No.  3232 

9l8 

b 

14.19 

13.24 

13.7 

27-5 

1894,  June  21 

919 

e 

14.75 

13.80 

14.4 

9h04m 

920 

c 

13.90 

12.95 

13.2 

26.9 

921 

c 

14.57 

13.62 

14.3 

28.3 

922 

c 

14.29 

13-34 

14.0 

27.7 

No.  3239 
1894,  June  22 

924 

925 

b 
b 

15.38 
14.99 

14-43 
14.04 

14.9 

14.5 

I0h07m 

926 

i 

14.31 

13.36 

13.8 

927 

k 

14.22 

13.27 

13.7 

028 

c 

14.25 

I  ^  ^O 

14.1 

OQ      C 

\J*4\J 

929 

e 

13.70 

12.75 

**T*  x 

13.2 

No.  3241 
1894,  June  23 

934 
935 

b 
e 

14.56 
14.40 

13.61 
13.45 



26.6 
25.9 



53-9 
53-3 

ioh54m 

No.  3245 

0^6 

a 

14.01 

13.96 

28.0 

1894,  June  25 

yO^J 

0-37 

e 

T"*V  •*• 

26.8 

vo/ 

14.46 

J^'CT 

27  2 

44  I 

0^0 

p- 

J.  J_|..£J.U 

M.CQ 

j^'ee 

*/  ••* 

28.0 

-(--f  •  A 
44.1 

040 

Q 
ff 

•Jv 
14.08 

13.13 

27  0 

=12  4 

No.  3247 

y^rj 
941 

& 

i 

Ai^..  \S^J 

14.60 

13.65 

17-2 

^/  .  w 

27.3  : 

1894,  June  27 

942 

i 

14-95 

14.00 

I6.7 

28.0 

9h53m 

943 

d 

15.00 

14.05 

I7.8 

28.1 

944 

f 

15.10 

14.15  i 

17.9 

28.3 

945 

b 

14-95 

14.00 

17.5   j 

28.0  1 

No.  3253 

936' 

a 

14.54 

13.59 

10.  1 

1894,  June  28 

946 

f 

14.14 

13.19 

9.8 

4no5m 

947 

c 

14.27 

13.32 

9.9 

948 

c 

13.46 

12.51 

9-3 

949 

c 

14.95 

14.00 

10.4 

1 

FROM    THE    MOTIONS    OF   THE    CALCIUM    FLOCCULI. 
TABLE  I.    Diurnal  Motions  of  the  Flocculi. — Continued. 


31 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No.  3253—Cont'd. 

950 

e 

I3.870 

I2.920 

9.6 

95i 

s 

14-95 

14.00 

10.4 

952 

g 

14-95 

14.00 

10.4 

953 

a 

14.41 

13.46 

10.  0 

954 

b 

14.54 

13-59 

10.  1 

955 

b 

14.14 

13.19 

9.8 

963 

c 

12.79 

11.84 

8.8 

964 

d 

15.48 

14.53 

10.8 

965 

h 

13-73 

12.78 

9-5 

No.  3258 

1894,  June  29 

9h55m 

No.  3265 

966 

f 

14-75 

13.80 

16.6 

27.0 

1894,  July  2 

f 

14.56 

I3.6l 

16.5 

IOhI2m 

968 

f 

14-39 

13-44 

16.3 

26.3 

969 

d 

14.23 

13.28 

16.1 

970 

a 

14.15 

13-20 

16.0 

971 

b 

14.19 

13.24 

16.1 

25.9 

972 

a 

13.82 

12.87 

15-6 

973 

b 

14.86 

13.91 

16.8 

27.2 

974 

b 

15.71 

14.76 

17.9 

976 

b 
b 

14.65 
14.75 

13.70 
13.80 

17.9 
16.7 

27.8 
27.0 

44-3 

No.  3272 
1894,  July  3 

977 
978 

a 
a 

14.39 
15.20 

13-44 
14.25 

II.  O 

10.6 

27.0 

3hIgm 

979 

S 

13.32 

12.37 

9-2 

980 

t 

13.84 

12.89 

9-6 

25.9 

981 

f 

13.99 

13.04 

9-7 

982 

c 

14.70 

13-75 

10.5 

27.6 

984 

c 

14.34 

13.39 

9.8 

26.9 

985 

a 

15.09 

14.14 

10.7 

28.4 

986 

f 

14.65 

13.70 

10.  0 

27.8 

41.6 

987 

a 

15.07 

14.12 

10.5 

No.  3279 

988 

a 

14.55 

13.60 

17.2 

1894,  July  4 

No.  3284 

990 

d 

14.64 

13.69 

13.0 

27.6 

1894,  July  5 

991 

f 

14.  7C 

I  7.  4Q 

12.8 

27.1 

r-3    Q 

3h30m 

992 

f 

•"t'OO 

14.38 

XO  •fv 

13.43 

12.9 

27.1 

993 

f 

14.34 

13.39 

13.1 

27.0 

994 

f 

14.20 

13.25 

13.0 

26.7 

995 

f 

14.14 

13.19 

12.6 

26.6 

996 

c 

14.38 

13.43 

12.5 

27.1 

No.  3286 

IOOI 

f 

14.89 

13.94 

14.9 

1894,  July  6 

1002 

h 

14.52 

13.57 

14.5 

2^I5m 

1003 

f 

13.96 

13.01 

13.9 

1004 

h 

14.80 

13.85 

14.8 

r 

No.  3293 

1005 

e 

17.  07 

13.02 

25.2 

1894,  July  7 

vv  3 

IOIO 

f 

xo.y/ 
14.69 

17.74 

26.6 

3h54m 

IOII 

h 

**T*wy 

14.74 

A  O  •  /T" 

26.7 

x^.  /  T" 

' 

THE   ROTATION    PERIOD    OF    THE    SUN    AS    DETERMINED 
TABLE  I.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No.  3295 

ion 

a 

I4.260 

1331° 

24.0 

38.1 

C-27 

1804.  July  o 

AV-'-LO 

1014 

a 

J.£f.^W 

1-2.40 

26.4 

O*-'*  A 
7Q.2 

oo  *  o 

67.2 

j.  k_jy_|.  j    j  nij     v/ 

1015 

a 

14.14 

O  *^f:7 

24.O 

ov  * 

\s  /  »« 

1016 

a 

T*F*  **t 

14.57 

1^.62 

26.? 

30.1 

1017 

c 

•*•*+•  D  / 

«,,2*w«' 

25.2 

Oy*  x 

±  wx  / 

1018 

c 

14-57 

1^.62 

25.7 

IOIQ 

g 

*«t«j/ 

14.62 

^O'"-" 

13.67 

25.8 

±\j  iy 
IO20 

e 

J-7     -7C 

25.2 

1022 

m 

12.82 

*-O'OJ 
11.87 

22.4 

102^, 

m 

12  40 

No.  3300 

J.\S^*J 

1025 

h 

14.41 

1««A|W 

13.46 

I3.I 

1894,  July  ii 

1026 

d 

15.00 

14.05 

13.9 

30.1 

43-4 

1104010 

1027 

h 

14.52 

13.57 

13.2 

IO28 

f 

14.21 

13.26 

12.9 

1029 

f 

14.21 

13.26 

12.9 

1030 

a 

15.03 

14.08 

13-7 

1031 

c 

14.72 

13.77 

13-4 

1032 

c 

15.24 

14.29 

13-9 

1033 

c 

14.42 

13.47 

12.8 

28.6 

41.6 

1034 

a 

14.95 

14.00 

13-8 

29.6 

1035 

a 

15-28 

14.33 

12.9 

30.3 

1036 

a 

14.82 

13.87 

13.0 

29.3 

1037 

c 

15-03 

14.08 

13.7 

1038 

c 

14.83 

13.88 

13.5 

1039 

f 

14.62 

13.67 

13.3 

1040 

f 

14.41 

13.46 

I3-I 

1041 

h 

14.52 

13.57 

13-2 

No.  3303 

1042 

g 

14.85 

13.90 

16.1 

29.4 

1894,  July  12 

1043 

g 

14.25 

13.30 

14.9 

28.1 

IIhOIm 

1044 
1045 

c 
a 

14.90 
14.95 

13.95 

14.00 

!5.6 
16.3 

29.5 
29.6 

1046 

a  +  c 

14.65 

13.70 

15.6 

1047 

a 

14.74 

13.79 

15.7 

1048 

h 

14.48 

13.53 

17.2 

28.6 

No.  3308 

1049 

e 

14.60 

17.74 

13.6 

40  4 

1  894,  July  13 

1050 

c 

^        ;J 
I4.O6 

XO  •  /  *T 

13.11 

12.8 

Cf\J»*f 

1051 
1052 

e 
d 

13.55 
14.98 

12.  6O 
14.03 

12.3 
13.7 

1053 

f 

14.57 

13.62 

13.3 

1054 

f 

14.37 

13.42 

13.1 

1055 

g 

14.26 

13.31 

13.0 

1056 

g 

13.96 

13.01 

12.7 

1057 

c 

14-57 

13.62 

13.3 

1058 

d 

14.37 

13.42 

13.1 

1059 

b 

15-39 

14.44 

14.1 

1060 

a 

14.26 

13.31 

13.0 

1061 

a 

14.98 

14.03 

13.7 

1062 

a 

15.09 

14.14 

13.8 

No.  3310 

1894,  July  14 

FROM    THE    MOTIONS    OF    THE    CALCIUM    FLOCCULI. 


33 


TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No.  3315 
1894,  July  16 

12*15911 

No.  3319 

1063 
1064 
1065 
1066 
1067 
1068 

1069 

b 

fd 
ff 

a 

d 

I5.250 
15.22 
I4.l6 
14.52 
14.90 
14-55 

1C.  20 

I4.300 
14.27 
13.21 
13.57 
13-95 
13.60 

14.  2C 

15.7 
15.4 
14.5 
14.9 
15.2 
14-3 

27.4 

26.3 
25.5 

27  Q 

42.7 
41.5 

1894,  July  17 

3h20m 

1070 
1072 
1073 
1074 

i 

ff 

13.50 
14.47 
14.96 
15.20 

12.55 
13.52 
14.01 

14.  2C 

10.3 
ii.  i 
ii.5 

27  Q 

No.  3320 
1894,  July  18 

1075 

1071 
1076 

d 

d 
a 

1441 

13.71 
14.43 

13.46 

12.76 
13.48 

14-5 
1C.  4 

27.8 

43-0 

54-0 

IIh02m 

1077 
1078 
1079 
1081 

d 
h 

f 

P 

14.76 
13-44 
13-97 
M.27 

I3.8I 
12.49 
13.02 

17.7,2 

15-7 
14.2 
14.8 

ICQ 

42.  C, 

1082 

e 

I4.O8 

I7.J7 

1C.  2 

41  .0 

1083 

e 

14.77 

13.82 

1C.  4 

44.1 

1084 

e 

14.21 

13.26 

14.9 

42.3 

No.  3326 

1085 
1089 
1090 
1091 

IOO2 

c 

i 
m 
k 

ff 

14-55 
I4.06 

13.53 
15.29 

14  00 

13.60 
13.11 
12.58 
14.34 

17  14 

15.5 
14.9 

J4-3 
16.3 

27  O 

1894,  July  19 

IOQ7 

h  +  ff 

14.  uy 
17  .eft 

4«5*^» 

12  OI 

2C  Q 

2hIQm 

No.  7777 

1094 
IIOI 

e 

or 

13.99 
14  60 

13.04 
17  6C 



^o-y 
27.6 

26  c 



52.1 

1894,  July  21 

oho  ^m 

1  102 

1  107 

g 
or 

14.42 
14  04 

13.46 

17  00 



26.6 

2C   A 



53-4 

1104 
1107 
1108 

C 

g 

Of 

14.11 

14-33 
17.62 

I3.I5 
13.37 
12.6? 



^0-4 
26.3 
26.1 
24  6 



52.1 
53.i 

No.  3338 

1113 

IIIC 

J 

g 

J.O.V^ 

14.63 

14  71 

;;' 
13.67 

11      1% 



26.3 

27  o 



55-4 

69.0 

81.9 

1894,  July  23 

1116 

ff 

14  82 

13  86 

28  o 

2hI2m 

III7 

i 

13  68 

12.72 

2C  7 

1118 

e 

14.08 

17.12 

26  =; 

1119 

i 

13  86 

12  90 

2C  7 

70  2 

1  1  20 

k 

13  82 

12  86 

^O'/ 

26  o 

112? 

or 

IT.    76 

12.  80 

24  6 

TO.  7 

<2.1 

No.  3348 
1894,  July  25 

2h4Im 

1  125 
1126 

1127 
1128 

1129 
1130 

1131 
1132 

e 

g 
t 
t 

d 
d 
c 
c 

13.78 
13-68 
14.07 

13.97 
14.67 
14.50 
14-97 
14-57 

12.82 
12.72 
13-11 
13.01 
I3.7I 
13-54 
14.01 
I3.6I 

12.4 

12.  1 
I3-I 
13.6 
M.3 
13.7 
14.2 
13-8 

25-9 

25-7 
26.5 
26.3 
27.7 

34  THE   ROTATION    PERIOD    OF   THE   SUN    AS    DETERMINED 

TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

i 

2 

3 

4 

5 

6 

No.  3348—  Cont'd. 

H33 

c 

I3.870 

12.91° 

13-1 

H34 

g 

14.07 

13.11 

13.3 

H35 

e 

13.19 

12.23 

12.4 

1136 

a 

15.26 

14.30 

14.5 

28.9 

No.  3354 
1894,  July  26 

1138 
H39 

g 
g 

14.38 
14.57 

13-42 
I3.6l 

13-5 
13.7 

2hs8m 

1140 

g 

14-57 

I3.6l 

13.7 

1141 

d 

15.07 

14.11 

14.2 

1142 

f 

15-37 

14.41 

14-5 

1143 

f 

14.86 

13.90 

14.0 

1  144 

i 

13.08 

12.12 

12.2 

H45 
1146 

e 
g 

13.87 
14.07 

12.91 
13.11 

13.0 
13.2 

1147 

g 

14.07 

13-11 

13-2 

No.  3355 

1894,  July  27 

3h07m 

No.  3366 

1  140 

e 

14  01 

I?  CK 

24  O 

1804    Tulv  ^o 

±  -i-fy 

i  mo 

i 

l^.Ul 

14  OO 

AO  "W«J 

n.io 

•**t*y 

2C  0 

iuyij.,    j  uij    £\j 

Th48m 

J.  A  ^\J 

Iici 

e 

•>•  *("*•"-' 

14  70 

•"•O-  J-w 

n.8^ 

26:° 

40.  Z 

J.     i^\J 

•*•   o 
IIC2 

g 

LLT*  /  y 

14  40 

XO  >WO 

17.44 

2^   ^ 

T'^'O 

52.8 

*  A  O^ 
HC7 

g 

•LT>»iT^/ 

14  08 

*  O  •T'T' 

1^.12 

•^O'O 
2^  7 

^84 

J***v' 

No.  3374 

*  *  oo 

1154 

c 

l.£f  «WJ 

14.86 

*  o  ••*•** 

13.90 

14.0 

•^o*/ 

28.2 

1894,  Aug.  i 

1155 

g 

12.94 

11.98 

12.2 

iih37m 

1161 

e 

14.64 

13.68 

I4.I 

27.7 

1162 

e 

13-93 

12.97 

13.2 

1163 

a 

15.11 

14.15 

14.4 

1164 
1165 

a 
a 

15-11 
14.52 

14-15 
13-56 

14.4 
14.2 

27.4 

1166 

a 

14.71 

13.75 

14.0 

1167 

d 

14.52 

13-56 

13-8 

1168 

f 

13.83 

12.87 

I3.I 

1170 

a 

14.22 

13.26 

13.5 

1171 

a 

14.61 

13.65 

13.9 

1172 

c 

14.76 

13-80 

14.2 

27.9 

No.  3382 

H73 

e 

14.46 

13-50 

13-6 

28.5 

1894,  Aug.  2 

1174 

i 

13.72 

12.76 

12.8 

I2h03m 

H75 

i 

14.01 

13-05 

I3.I 

1176 

e 

15.01 

14.05 

I4.I 

1177 

e 

14.61 

13.65 

13.7 

1178 

c 

14.51 

13.55 

13-6 

1179 

g 

14.71 

13.75 

13-8 

1180 

a 

14.81 

13.85 

13.9 

1181 

c 

14.81 

13.85 

13.8 

29.2 

1182 

c 

14.41 

13-45 

13-5 

1183 

a 

14.11 

13-15 

13.7 

27.7 

1184 

e 

14.19 

13-23 

12.7 

27.9 

1185 

a 

15.00 

14.04 

13.7 

29.6 

1186 

g 

14.21 

13-25 

13.3 

1188 

g 

14.11 

13-15 

13.2 

1189 

c 

14.11 

13-15 

13.2 

FROM    THE   MOTIONS   OF   THE   CALCIUM    FLOCCULI. 


35 


TABLE  I.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

i 

2 

3 

4 

5 

6 

No.  3388 

II9I 

f 

15-01° 

14.05° 

15-5 

1894,  Aug.  3 

1192 

a 

16.01 

15.05 

16.6 

I2ho8m 

H93 

a 

16.36 

15.40 

17.0 

No.  3394 

1  104 

h 

14.62 

13.66 

28.4 

40.6 

1804    Aufir   4 

A  Ay  -4- 

14.67 

13.71 

28.2 

40.8 

i  Ljy^|  j    ^&.ug^»    ^-f 

1106 

ft 

**?•*"'/ 

14.47 

27.3 

No.  3398 

1197 

d 

**f  «*f/ 

14.60 

13.64 

13.0 

1894,  Aug.  6 

1198 

d 

14.50 

13.54 

12.9 

3h07m 

1199 
1  200 

c 
c 

14.71 
15-44 

13.75 
14.48 

13^8 

1  201 

c 

14.89 

13.93 

13.5 

27.5 

1202 

c 

14.50 

13.54 

12.9 

1203 

c 

14.82 

13-86 

13.6 

27.5 

39-4 

I2O4 

c 

15.12 

I4.l6 

13-8 

28.4 

40.2 

1205 

c 

15.44 

14.48 

13-8 

1207 

e 

15-44 

14.48 

13-8 

1209 
1210 

c 
c 

14.25 
14.76 

13.29 
13.80 

12.5 
12.7 

26.2 
27.4 

37-7 
39-2 

I2II 

e 

14.37 

13.41 

13.5 

27.2 

38.2 

1212 

g 

13.48 

12.52 

12.2 

24.8 

1213 
1214 

c 
e 

14.39 
14.64 

13.43 
13.68 

12.7 
13-0 

26.5 
27.0 

1216 

a 

15.13 

14.17 

13.5 

1217 

a 

15.13 

14.17 

13.5 

1218 

a 

15.02 

14.06 

13-4 

1219 

S 

13.84 

12.88 

12.8 

25.2 

36.6 

1222 

c 

13.73 

12.77 

13.0 

25.2 

1223 

c 

14.92 

13.96 

13-3 

No.  3405 

I2O6 

g 

14.64 

13-68 

13-3 

25-8 

1894,  Aug.  7 

1215 

c 

14.73 

13.77 

13.7 

26.0 

ih59m 

1220 

c 

14.98 

14.02 

14.3 

1221 

e 

14.20 

13.24 

13-5 

1224 

c 

14.79 

13.83 

I4.O 

26.1 

1225 

g+i 

13.71 

12.75 

13.0 

1226 

e 

14.69 

13.73 

14.0 

1227 

c 

15.28 

14.32 

14.3 

27.0 

1229 

a 

15.36 

14.40 

15.2 

27.2 

No.  3411 

1230 

e 

15.39 

14.43 

12.5 

1894,  Aug.  8 

1231 

c 

14.93 

13.97 

12.  1 

2n28m 

1232 

e 

15.05 

14.09 

12.2 

1233 

e 

14.01 

13-05 

ii.  3 

1234 

d 

15.16 

14.20 

12.3 

1236 

d 

14-93 

13.97 

12.  1 

1237 

c 

14.93 

13-97 

12.  1 

No.  3417 

1894,  Aug.  9 

No.  3424 

1239 

f 

14.16 

13.20 

28.1 

1894,  Aug.  14 

1240 

f 

13.83 

12.87 



27.4 

ioh56m 

1241 

d 

14.25 

13.29 



28.3 

36  THE   ROTATION    PERIOD    OF    THE    SUN    AS   DETERMINED 

TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

i 

2 

3 

4 

5 

6 

No.  3424—  Confd. 

1242 

C 

14.96° 

14.00° 

29.8 

1243 

a 

14.49 

13.53 



29.2 

42.0 

1249 

e 

14.28 

13.32 

28  4 

41.4 

12^1 

d 

14.02 

I  -3  06 

27  8 

*T*    " 

J--&3  i 

12^2 

o 

j.  ^  .  w\^ 
12  77 

^  /  .u 

27  2 

No.  3429 

A-fi'O 
1253 

& 

e 

14.12 

'  /  / 

I3.I6 

13.3 

*"i  ** 

24.4 

1894,  Aug.  16 

1254 

e 

14.05 

13.09 

13-4 

24.3 

2h°2m 

1255 
1256 

c 
c 

14.11 
13.89 

13.15 
12.93 

12.9 
12.7 

24.0 

1257 

e 

14.64 

13.68 

13.5 

25-4 

1258 

g 

14.42 

13.46 

13.2 

1259 

i 

14.31 

13-35 

13-1 

I26O 

i 

14.72 

13.76 

13.5 

I26l 

h 

I4.8l 

13.85 

13-5 

25.7 

1263 

m 

13.60 

12.64 

12.4 

1264 

f 

14.01 

13.05 

12.8 

1265 
1266 

ff 

13.99 
15.03 

13.03 
14.07 

12.0 

13.8 

24.2 

1267 

f 

13.70 

12.74 

12.5 

No.  3439 

1268 

e 

15.02 

14.06 

12.3 

1894,  Aug.  17 

1269 

e 

14.45 

13-49 

1  1.  8 

Ih35m 

1270 

d 

15.02 

14.06 

12.3 

1271 

h 

14.67 

I3.7I 

12.0 

1272 

d 

15.25 

14.29 

12.5 

1273 

h 

15.13 

14.17 

12.4 

1274 

c 

14.79 

13.83 

12.  1 

1275 

c 

14,67 

13.71 

I2.O 

1276 

1277 

a 
a 

15-47 
14.67 

I4.5I 
13.71 

12.7 

12.0 

1278 
1280 

a 
b 

15.70 
15.02 

14.74 
14.06 

12.9 

12.3 

1282 

e 

13.76 

12.80 

II.  2 

1283 

i 

14.56 

13.60 

11.9 

1284 

0 

11.70 

10.74 

9.4 

1285 

m 

12.73 

11.77 

10.3 

1286 

k 

13-53 

12.57 

II.  0 

1287 

q 

13-53 

12.57 

II.  0 

No.  3441 

1894,  Aug.  18 

ioh35m 

No.  3447 

1288 

h 

14.48 

13.52 

13.6 

1894,  Aug.  21 

1289 

d 

14.36 

13.40 

13.5 

26.9 

I0h52m 

1290 

b 

14.18 

13.22 

13.3 

1291 

c 

14.88 

13.92 

14.0 

1292 

e 

14.48 

13.52 

13.6 

1293 

c 

13.98 

13.02 

13.1 

f 

14.48 

13-52 

13.6 

1296 

j 

14.78 

13.82 

13.9 

1297 

j 

14.68 

13.72 

13.8 

1298 

d 

14.38 

13.42 

13.5 

1299 

e 

13-93 

12.97 

13.8 

26.0 

1300 

f. 

13.98 

13.02 

13.1 

1305 

i 

13.29 

12.33 

12.4 

FROM    THE    MOTIONS    OF   THE   CALCIUM    FLOCCULI. 


TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

f 

6 

No.  3453 

1307 

i 

I3.270 

12.31° 

12.3 

1894,  Aug.  22 
IlhOOm 

1308 
1309 

b 

g 

14-77 
14.28 

I3.8I 
13.32 

13.8 
13.6 

28.2 

1310 

i 

14-37 

13.41 

13-7 

28.4 

1311 

i 

14.27 

13.31 

13-3 

1312 

g 

14.27 

13.31 

13-3 

1313 

s 

14-57 

I3.6I 

13.6 

1314 

i 

14.17 

13.21 

13.2 

1316 

g 

14.37 

13.41 

13.4 

1317 

g 

14-57 

I3.6l 

13.6 

1318 

e+g 

14.75 

13-79 

14.0 

29.2 

1319 

g 

14.14 

I3.I8 

13.4 

27.9 

No.  3456 

1320 

i 

13.88 

12.91 

14.9 

26.2 

1894,  Aug.  23 

1321 

d 

14.30 

13-34 

14.9 

ioh59m 

1322 

k 

13-94 

12.98 

14.5 

1323 

m 

13.85 

12.89 

14.4 

1324 

h 

14.12 

13.15 

14.3 

26.6 

1325 

K 

13-68 

12.72 

14.2 

No.  3462 

1326 

d 

14.22 

13.25 

12.0 

1894,  Aug.  24 

1327 

f 

14.22 

13.25 

12.0 

ih47m 

1328 

i 

13.34 

12.37 

II.  2 

1329 

m 

13.89 

12.92 

ii.  7 

1330 

i 

13.01 

12.04 

10.9 

1332 

k 

13.78 

12.81 

n.6 

1333 

b 

14.33 

13.36 

12.  1 

1334 

b 

I4.OO 

13.03 

11.8 

No.  3464 

1894,  Aug.  25 

nh3im 

No.  3467 

1335 

a 

14.24 

13.27 

13.2 

1894,  Aug.  31 

1337 

b 

14.14 

13.17 

13.1 

2hI8m 

1338 

g 

13-94 

12.97 

12.9 

1339 

k 

12-53 

11.56 

H.5 

1340 

g 

14.04 

13.07 

13-0 

1341 

c 

14-95 

13.98 

13-9 

1342 

c 

14.24 

13.27 

13-2 

1344 

e 

14.24 

13.27 

13-2 

1345 

a 

14.14 

13.17 

13-1 

1346 

i 

14-34 

13.37 

13-3 

1347 

a 

14.85 

13.88 

13-8 

1348 

g 

13.94 

12.97 

12.9 

1349 

f 

14.24 

13.27 

13.2 

1350 

h 

13-74 

12.77 

12.7 

No.  3473 

1894,  Sept.  i 

2hI0m 

No    ^476 

I-JCC 

d 

17.  60 

12.72 

38.1 

A!  v«     ^L^f\J 

1804.  Scot.  * 

^OOu 
I7C6 

m 

J.J.V.7V, 
13.67 

12.70 

26.1 

37-9 

j.uvy£f.}    w^\^^u.    j 

2n26m 

*O  Jw 

1^7 

tn 

I  -3    QQ 

1^  02 

26.6 

*J/       ^7 

^8.0 

iOJ/ 

*-o'yy 

AO  •*-''•' 

o^j  *  y 

38  THE   ROTATION    PERIOD    OF   THE   SUN    AS    DETERMINED 

TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No.  3479 

1894,  ^Sept.  7 

No.  3488 
1894,  Sept.  17 

1377 
1378 

d 
d 

14.91° 
14.91 

13.93° 
13.93 

15-0 
I5.I 

27.6 
27.6 

2h32m 

1379 

d 

14.91 

13-93 

14.8 

1380 

d 

15.85 

15-8 

1381 

f 

14.46 

13.48 

14.5 

26.7 

1382 

d 

15.31 

14-33 

15.6 

28.4 

1383 

b 

15.19 

14.21 

I5-I 

1384 

e 

15.10 

14.12 

15.0 

1385 

i 

14.05 

13.07 

14.4 

25-9 

1386 

i 

14.15 

13.17 

14-3 

26.1 

1387 

i 

13.70 

12.72 

14.0 

25.2 

1388 

I 

I3.58 

26  9 

iO'-"-' 

1389 

i 

14.40 

13.42 

14.3 

26.6 

1300 

a 

13  ^7 

M.-3 

27  0 

67  6 

•"•Ob/*-' 

1391 

b 

14.75 

o  *o/ 

13.77 

•O 
14.4 

•*/  •** 

27.3 

\j  /  »\j 

1392 

b 

14.34 

13.36 

14.2 

1393 

a 

15.10 

14.12 

15.0 

1394 

a 

14.72 

13.74 

14.6 

1395 

d 

14.65 

13.67 

15.0 

27.1 

1396 

f 

14.65 

13.67 

14.6 

27.1 

1397 

f 

14.06 

13.08 

13-9 

1398 

f 

15.10 

14.12 

15-0 

1399 

I 

14.15 

13.17 

I5-I 

26.1 

1400 

j 

13.69 

12.71 

13-5 

1401 

14-35 

13-37 

14.6 

26.5 

1402 

i 

15-00 

14.02 

14.9 

1403 

b 

14.72 

13-74 

14.6 

1404 

d 

14.76 

I3.78 

14.7 

27.3 

1405 

a 

14.82 

13.84 

14.7 

1406 

n 

13-35 

12.37 

13.0 

24.5 

1407 

b 

14.56 

13.58 

14.5 

26.9 

1408 

b 

14.58 

13.60 

14.9 

27.2 

67.7 

No.  3493 

1409 

k 

14.27 

13.29 

12.2 

**/  " 

w/  '  / 

1894,  Sept.  18 

1410 

k 

13.51 

12-53 

H-5 

4h03m 

1412 

f 

14.38 

13.40 

12.3 

1413 

h 

13.83 

12.85 

ii.  8 

1414 

I 

13.83 

12.85 

1  1.  8 

No.  3498 

1894,  Sept.  19 

2h05m 

No.  3503 

1417 

t[ 

13.70 

12.72 

23.0 

37.6 

1894,  Sept.  22 

1418 

o 

p 

13.06 

24.8 

39.2 

' 

-L4"T  X1-/ 

1419 

& 

s 

n'.SS 

10.90 

.....1 

20.5 

O;J  ••** 

No.  3507 
1894,  Sept.  24 

I42O 
1421 

g 

e 

13.75 
13.40 

12.77 
12.42 

14.3 
13.9 

I0h53m 

1422 

a 

14.20 

13.22 

14.9 

28.2 

1423 

a 

14.34 

13.36 

14.9 

28.5 

1424 

a 

14.77 

13.79 

15-3 

29.4 

FROM    THE    MOTIONS    OF    THE    CALCIUM    FLOCCULI. 
TABLE  i.    Diurnal  Motions  of  the  Flocculi. — Continued. 


39 


Plate  No.  and  date. 

No. 

Zone 

Diurnal 
motion, 
sidereal. 

Diurnal 
motion, 
synodic. 

I 

2 

3 

4 

5 

6 

No.  3507  —  Confd. 

1425 

a 

I4.380 

I3.400 

14.7 

28.6 

1426 

g 

14.44 

13.46 

14.8 

28.7 

1427 

d 

14-74 

13.76 

15.4 

No.  3509 

1428 

e 

14.48 

I3.50 

13.7 

1894,  Sept.  25 

1429 

e 

I4.I8 

13.20 

13-4 

ih45m 

1430 

g 

13.79 

I2.8I 

13-0 

1431 

e 

14.58 

I3.60 

13-8 

1432 

d 

13.69 

12.71 

12.9 

1433 

h 

14.18 

13-20 

13.4 

1434 

h 

14.58 

13.60 

13.8 

1436 

c 

14.58 

13.60 

13.8 

No.  3516 

1894,  Sept.  26 

2ho6m 

No.  3528 

1438 

e 

14.33 

13-35 

ii.  i 

1894,  Sept.  28 

1439 

e 

14-57 

13-59 

II  .3 

2h34m 

1440 

c 

14-93 

13-95 

11.6 

1441 

c 

14.45 

13.47 

II.  2 

1442 

h 

1445 

13.47 

II.  2 

1443 

h 

14.09 

13.11 

10.9 

1444 

f 

14.33 

13.35 

II.  I 

1445 

h 

13.85 

12.87 

10.7 

1447 

h 

14.69 

13.71 

11.4 

1448 

b 

15.05 

14.07 

11.7 

1449 

a 

13-97 

12.99 

10.8 

1450 

a 

14.45 

13-47 

II.  2 

1451 

e 

14.21 

13.23 

II.  0 

1452 

c 

14.21 

13.23 

II.  O 

1453 

a 

I4.8I 

13.83 

II-5 

1454 

c 

I5.I8 

14.20 

11.8 

No.  3533 

1894,  Sept.  29 

ioh3im 

The  diurnal  motions  (|)  of  all  the  flocculi  lying  within  each  zone  five 
degrees  wide  are  grouped  in  table  2.  The  mean  diurnal  motion  for  each 
zone,  together  with  its  probable  error,  and  the  equivalent  rotation  period  in 
days,  are  also  given.  In  deriving  the  mean,  the  diurnal  motions  are  weighted 
according  to  the  interval  in  days. 


40  THE   ROTATION    PERIOD    OF   THE    SUN    AS    DETERMINED 

TABLE  2.    Diurnal  Motions  Corresponding  to  each  Five-Degree  Zone. 


[Zone  a  =  o°  to  5°.           Mean  Diurnal  Motion  ==  14.72°  ±  0.031.] 

Diurnal 

Diurnal 

Diurnal 

Diurnal 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

98 

I 

I4.670 

819' 

I 

14.64° 

1030 

I 

15-03° 

H93 

I 

16.36° 

106 

5 

14.62 

820 

I 

14.92 

1034 

2 

14-95 

1216 

I 

15.13 

104 

3 

13.56 

821 

2 

14.35 

1035 

2 

15.28 

1217 

I 

15.13 

91 

i 

14.06 

827 

2 

14-59 

1036 

2 

14.82 

1218 

I 

15-02 

107 
302 

2 
2 

13.80 
14.57 

842 
853 

4 
3 

15.00 
14.75 

1045 
1046 

2 

14-95 
14.65 

1229 

1243 

2 

3 

15.36 
14.49 

410 

I 

14-34 

877 

3 

14-49 

1047 

14.74 

1276 

i 

15-47 

411 

I 

14.79 

898 

2 

14-59 

1060 

14.26 

1277 

I 

14.67 

455 

I 

15.05 

899 

2 

14.21 

1061 

14.98 

1278 

i 

15.70 

472 

I 

I4.3I 

936 

2 

14.91 

1062 

15.09 

1335       I 

14.24 

470 

2 

14.90 

936' 

I 

14.54 

1068 

3 

14-55 

1345 

i 

14.14 

477 

2 

14.48 

953 

I 

14.41 

1076 

3 

14-43 

1347 

I 

14.85 

491 

3 

14.46 

970 

I 

14.15 

1136 

2 

15.26 

1390 

5 

14-55 

507 

14.20 

972 

I 

13.82 

1163 

I5-II 

1393 

i 

15.10 

553 

14.99 

977 

2 

14.39 

1164 

15-11 

1394 

i 

14.72 

554 

15.48 

978 

I 

15.20 

1165 

14.52 

1405 

i 

14.82   | 

588 

13.84 

985 

2 

15.09 

1166 

14.71 

1422 

2 

14.20 

608 

2 

14.70 

987 

I 

15.07 

1170 

14.22 

1423 

2 

14-34 

671 

13.80 

988 

I 

14.55 

1171 

I4.6l 

1424 

2 

14.77 

674 

14.70 

1013 

4 

14.26 

1180 

I4.8I 

1425 

2 

14.38 

731 

I 

15.06 

1014 

5 

14.44 

1183 

2 

14.11 

1449 

I 

13.97 

743 

I 

14.95 

1015 

2 

14.14 

1185 

2 

15.00 

1450 

I 

14-45 

761 

I 

14.30 

1016 

3 

14.57 

1192 

I 

16.01 

1453 

I 

I4.8I 

785 

4 

14.34 

[Zone   b  =  o°   to—  5°.           Mean   Diurnal    Motion  =  14.57°  ±  0.045.] 

32 

i 

13.99° 

458 

3 

I4.090 

882 

I 

14.78° 

1063 

i        I5.25°i 

34' 

2 

14.72 

489 

3 

14.52 

897 

2 

14.92 

1093 

2 

13.56 

38 

I 

15.24 

672 

i 

14.80 

918 

2 

14.19 

1280 

I 

15.02 

36' 

2 

I3.8I 

673 

i 

13.80 

924 

I 

15-38 

1308 

I 

14.77 

36" 
38'" 

2 
I 

14.26 
14.57 

719 
733 

5 
i 

14.40 
14.62 

925 
934 

I 

4 

14.99 
14.56 

1290 
1333 

I 
I 

14.18 
14-33 

52 

5 

14.75 

732 

2 

14.24 

945 

2 

14-95 

1334 

I 

14.00 

53' 

i 

14-73 

749 

I 

14.71 

954 

I 

14.54 

1337 

I 

14.14 

55 

5 

14.68 

75i 

I 

14.60 

955 

I 

14.14 

1383 

I 

15.19 

87 

2 

14.66 

793 

2 

15.13 

971 

2 

14.19 

I39i 

2 

14-75 

217 

15.12 

828 

I 

14.73 

973 

2 

14.86 

1392 

I 

14-34 

225 

i    13.88 

850 

2 

15.34 

974 

I 

15-71 

1403 

I 

14.72 

230 

12.37 

879 

I 

15.20 

975 

3 

14.65 

1407 

2 

14.56 

264 

I5.I8 

880 

I 

14.64 

976 

2 

14.75 

1408 

5 

14.58 

315 

i    15.84 

881 

I 

14.50 

1059 

I 

15.39 

1448 

i 

15.05 

361 

14.30 

[Zone  c  =  5°  to  10°.            Mean  Diurnal  Motion  =  14.50°  ±  0.027.] 

i         3 

I4.740 

183 

I3.55°ii     447 

3 

14.07° 

572 

i 

14-34° 

19         3 

14.84 

184 

15-45 

448 

i 

14.22 

577 

2 

14.24 

i' 

3 

14.62 

38i 

15.84 

450 

i 

14.42 

578 

2 

14.24 

37' 

3 

14.37 

382 

14.30 

451 

i 

14.78 

670 

I 

14.70 

78 

2 

14.33 

386 

13.69 

452 

i 

14.42 

693 

I 

14-37 

82 

I 

15.13 

407 

14.98 

456 

3 

14.76 

702 

2 

14.64 

106' 

I 

14.40 

415 

14.60 

552 

2 

15.01 

703 

2 

14.40 

132 

5 

13.70 

422 

14-79 

57i 

I 

13-97 

704 

2 

14.49 

FROM    THE    MOTIONS    OF    THE    CALCIUM    FLOCCULI. 


41 


TABLE  2.    Diurnal  Motions  Corresponding  to  each  Five-Degree  Zone. — Continued. 


[Zone  c  =  5°  to  10°.           Mean  Diurnal  Motion  =  14.50°  ±  0.027.  —  Continued.] 

Diurnal 

Diurnal 

Diurnal 

Diurnal 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

721 

I 

I2.9I0 

904 

3 

14.44° 

1057 

14-57° 

1222 

2 

I3.730 

722 

I 

13.51 

912 

3 

14.47 

1085 

14.55 

1223 

I 

14.92 

726 

2 

14.49 

921 

2 

14-57 

1104 

<• 

14.11 

1215 

2 

14.73 

740 

2 

14.50 

922 

2 

14.29 

1131 

14.97 

1220 

I 

14.98 

758 

I 

13.25 

92O 

2 

13.90 

1132 

14-57 

1224 

2 

14.79 

760 

I 

14.15 

928 

3 

14.25 

H33 

13.87 

1227 

2 

15.28 

762 

I 

14.98 

947 

I 

14.27 

H54 

2 

14.86 

1231 

I 

14.93 

768 

I 

14.30 

948 

I 

13.46 

1172 

2 

14.76 

1237 

I 

14.93 

776 

I 

14.10 

949 

I 

14.95 

1178 

I 

14.51 

1242 

2 

14.96 

779 

I 

14.59 

963 

I 

12.79 

1181 

2 

I4.8l 

1255 

I 

14.11 

784 

4 

14.53 

982 

2 

14.70 

1182 

I 

14.41 

1256 

2 

13.89 

822 

i 

14.64 

984 

2 

14.34 

1189 

I 

14.11 

1274 

14.79 

823 

i 

14.82 

996 

2 

14.38 

1199 

I 

14.71 

1275 

14.67 

825 

i 

14.36 

1017 

2 

14.30 

1  200 

I 

15.44 

1291 

14.88 

826 

i 

14.45 

1018 

2 

14.57 

1201 

2 

14.89 

1293 

13.98 

822' 

i 

14-73 

1031 

I 

14.72 

1202 

I 

14.50 

1341 

14-95 

843 

4 

14.70 

1032 

I 

15.24 

1203 

3 

14.82 

1342 

14.24 

861 

i 

14.52 

1033 

3 

14.42 

1204 

3 

15.12 

1436 

14.58 

862 

i 

15.14 

1037 

i 

15.03 

1205 

i 

15.44 

1440 

I 

14-93 

872 

i 

13.99 

1038 

i 

14.83 

1209 

3 

14.25 

1441 

I 

14-45 

873 

3 

14.17 

1044 

2 

14.90 

I2IO 

3 

14.76 

1452 

I 

14.21 

891 

2 

14.28 

1046 

I 

14.65 

1213 

2 

14.39 

1454 

I 

I5.I8 

903 

2 

14.76 

1050 

I 

14.06 

[Zone  d  =  —  5°  to  —  10°.            Mean  Diurnal  Motion  =  14.55°  ±  0.030.] 

27 

3 

I4.420 

364 

I 

I4.390 

750 

I 

15-39° 

1093 

2 

13.56° 

36 

2 

14.62 

365 

I 

13.69 

773 

I 

14.49 

1116 

2 

14.82 

35 

3 

15.87 

387 

I 

13.52 

792 

2 

14.57 

1129 

2 

14.67 

5i 

5 

14.69 

394 

I 

13.69 

795 

2 

14.27 

1130 

14.50 

Si' 

3 

14-93 

417 

I 

14.44 

805 

I 

14.21 

1141 

15.07 

57' 

I 

14.78 

418 

I 

15.08 

829 

I 

15-11 

1167 

14.52 

50 

2 

15.08 

457 

I 

13-54 

841 

3 

14.82 

1197 

14.60 

75 

2 

14.03 

459 

3 

14.03 

866 

i 

15.05 

1198 

14.50 

109 

2 

I4.52 

461 

i 

I4.3I 

876 

3 

14.15 

1234 

I5.l6 

138 

6 

14.58 

468 

i 

I3.8I 

878 

i 

13.80 

1236 

14-93 

168 

4 

14.64 

469 

i 

13-54 

883 

i 

15.20 

1241 

14.25 

168' 

4 

14.75 

487 

2 

14.52 

894 

2 

14-43 

1251 

14.02 

165' 

3 

I4.52 

488 

3 

14.52 

896 

2 

14.54 

1270 

15.02 

165 

i 

14.06 

5M 

2 

14.50 

943 

2 

15.00 

1272 

15.25 

228 

i 

14.46 

522 

2 

15.10 

964 

I 

15.48 

1289 

14.36 

232 

3 

14.72 

520 

I 

14.24 

969 

I 

14.23 

1298 

14.38 

242 

3 

14.48 

530 

2 

14.87 

990 

2 

14.64 

1321 

14.30 

258 

i 

14.87 

531 

2 

14.60 

1026 

3 

15.00 

1326 

14-22 

259 

i 

14.42    j 

615 

I 

14.56 

1052 

i 

14.98 

1355 

3 

13.69 

261 

i 

15.03 

631 

I 

14.06 

1058 

i 

14-37 

1377 

2 

14.91 

304 

3 

13.62    I 

634 

I 

13.98 

1065 

I 

I4.l6 

1378 

2 

14.91 

314 

i 

14.41 

635 

I 

13.89 

1069 

2 

15.20 

1379 

I 

14.91 

316         i 

14.12 

644 

I 

13.69 

1073 

I 

14.96 

1380 

I 

15.85 

347         3 

14.06 

677 

I 

15.00 

1074 

2 

15.20 

1382 

2 

15.31 

356     |     3 

15.19    ! 

733 

I 

14.62 

1075 

4 

14.41 

1395 

2 

14.65 

357         4 

I4-I3 

748 

3 

14.98 

1071 

i 

13.71 

1404 

2 

14.76 

358         4 

I4.l6 

744 

2 

14.87 

i  1077 

i 

14.76 

1427         i 

14.74 

362         i 

14.30 

745 

2 

14.20 

!   1092 

2 

14.09 

1432         i 

13.69 

363          i 

14.20 

746 

2 

15-12 

42  THE   ROTATION    PERIOD    OF    THE    SUN    AS   DETERMINED 

TABLE  2.    Diurnal  Motions  Corresponding  to  each  Five-Degree  Zone. — Continued. 


[Zone  ^  =  10°  to  15°.            Mean  Diurnal  Motion  =  14.34°  ±  0.024.] 

Diurnal 

Diurnal 

Diurnal 

Diurnal 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
s  dereal. 

5' 

3 

14.42° 

559 

I 

15.29° 

902 

14.25° 

1176 

I 

15.01° 

2 

14.02 

567 

2 

13.56 

915 

13-99 

1177 

I 

I4.6l 

Af 

I 

14.38 

58i 

2 

14.24 

916 

14-75 

1184 

2 

14.19 

2' 

4 

14.42 

641 

I 

13-57 

919 

14-75 

1207 

I 

15-44 

33 

2 

14.78 

675 

I 

13.70 

895 

14.58 

I2II 

3 

14.37 

23' 

I 

14.15 

694 

I 

14.03 

929 

13.70 

1214 

2 

14.64 

42 

I 

14.73 

695 

I 

14.60 

935 

4 

14.40 

1221 

I 

14.20 

42' 

2 

14.19 

699 

2 

14-54 

937 

2 

I4.3I 

1226 

I 

14.69 

44 

3 

13.69 

724 

I 

13.92 

950 

I 

13.87 

1230 

I 

15-39 

44' 

2 

14.41 

725 

4 

14.02 

1005 

2 

13.97 

1232 

I 

15.05 

56' 

I 

13.93 

737 

3 

14.20 

1019 

2 

14.62 

1233 

I 

I4.OI 

71 

I 

14.58 

738 

i 

13.51 

1020 

2 

14.30 

1249 

3 

14.28 

78' 

2 

14.71 

739 

i 

14.23 

1049 

3 

14.69 

1253 

2 

14.12 

84 
129 

3 

3 

15.27 
14.10 

727 
764 

i 
i 

14.42 
14.98 

1051 
1082 

I 

3 

13.55 
14.08 

1254 

2 

2 

14.05 
14.64 

185 

i 

13.99 

765 

i 

14.20 

1083 

3 

14.77 

1268 

15.02 

223 

2 

14.63 

767 

i 

14.20 

1084 

3 

14.21 

1269 

14-45 

233 

I 

14.82 

780 

i 

1449 

1094 

4 

13-99 

1282 

13.76 

252 

2 

I4.6l 

781 

2 

14.41 

HIS 

2 

I4.3I 

1292 

14.48 

253 

4 

14.15 

782 

2 

14.20 

1118 

2 

14.08 

1299 

13-93 

268 

3 

14.79 

783 

2 

14.30 

1125 

2 

13.78 

I3l8 

14-75 

289 

4 

14.12 

786 

2 

14.52 

H35 

I 

13.19 

1344 

14.24 

344 

3 

14.06 

790 

2 

13.87 

H45 

I 

13.87 

1384 

15.10 

405 
406 

i 
i 

14.89 
14.98   1 

798 
807 

I 
I 

14.21 
14.51 

1149 
1151 

2 

3 

14.01 
14.79 

1421 
1428 

13.40 
14.48 

412 

i 

15.28    1 

824 

I 

14-45 

1152 

4 

14.40 

1429 

I4.I8 

414 

i 

14.70 

869 

I 

14.26 

H53 

3 

14.08 

1431 

14.58 

429 

i 

14.51 

871 

I 

I4.6l 

1161 

2 

14.64 

1438 

14.33 

428 

i 

15.38    i 

874 

5 

14.30 

1162 

I 

13-93 

1439 

14.57 

499 

i 

13.54    i 

901 

i 

14.25 

H73 

2 

14.46 

1451 

14.21 

548 

i 

15.27 

i 

[Zone  f  =  —io°  to  —15°.           Mean  Diurnal  Motion  =  14.39  ±  0.020  •] 

18 

2 

I4.260 

248         6 

14.96° 

373 

I5.I70 

535 

I 

I4.700 

26' 

I 

14.41 

249 

i 

12.98 

374 

14.67 

56o 

4 

14.60 

54 

4 

14.57 

251 

4 

14.33 

420 

14.60 

568 

4 

14.41 

60 

3 

14.01 

260 

i 

15.32 

467 

I4.I3 

555 

4 

14.01 

61 

4 

14.14 

263 

i 

15.32 

468 

I3.8I 

574 

3 

14.09 

64' 

i 

13.97 

265 

i 

14.06 

474 

14.13 

585 

I 

15.70 

79 

2 

13.74 

297 

3 

14.69 

483 

5 

13-97 

586 

3 

14.01 

92 

2 

14.67 

298 

3 

14-88 

484 

5 

13.87 

587 

3 

14.08 

99 

I 

14.67 

304 

3 

13.62 

485 

5 

13.84 

589 

i 

15.39 

93' 

I 

13.65 

305 

3 

14.42 

486 

3 

14.27 

592 

3 

14.45 

103 
116 

3 

2 

13-97 
14.11 

326 

i 
i 

13.84 
13.74 

500 

3 
3 

14.43 
14.63 

596 
632 

i 

i 

14.80 
14.19 

124 

5 

14.14 

330 

i 

15.26 

505 

i 

15.34 

633 

14.09 

133 

4 

14.31 

353 

4 

14.26 

512 

2 

14.50 

636 

14.09 

141 

3 

14.40 

354 

3 

I4.6l 

515 

2 

14.39 

639 

14.19 

142 

i 

14.63 

355 

3 

14.52 

2 

13.80 

640 

14.40 

163 

5 

14.55 

360 

3 

14.44 

519 

I 

14.09 

650 

13-79 

145 

i 

12.78 

367 

i 

14.39 

523 

I 

12.99 

654 

14.70 

164' 

3 

15.01 

368 

i 

13.15 

524 

I 

13.98 

669 

14.80 

191 

i 

14.36 

372 

i 

14.77 

533 

2 

14.05 

678 

14.80 

i 

FROM    THE    MOTIONS    OF   THE    CALCIUM    FLOCCULI.  43 

TABLE  2.    Diurnal  Motions  Corresponding  to  each  Five-Degree  Zone. — Continued. 


[Zone  f  =  —  10°  to  15°.           Mean  Diurnal  Motion  =  14.39°  —  0.020.  —  Continued.] 

Diurnal 

Diurnal 

Diurnal 

Diurnal 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

682 

3 

14.22° 

832 

2 

14.87° 

967 

I 

14.56° 

1079 

I 

13-97° 

690 

i 

15.06 

833 

5 

14.36 

968 

2 

14-39 

IH3 

6 

14.63 

705 

2 

14.49 

839 

2 

14-43 

98! 

I 

13-99 

1142 

I 

15.37 

709 

2 

14.49 

840 

2 

14.65 

986 

3 

14.65 

H43 

I 

14.86 

710 

2 

14.49 

840' 

I 

15.01 

991 

4 

14-35 

1168 

I 

13.83 

711 

2 

14.30 

844 

2 

14.86 

992 

2 

14.38 

1191 

I 

15.01 

712 

2 

14.69 

845 

I 

14.32 

993 

2 

14-34 

H95 

3 

14.67 

713 

2 

14.64 

846 

I 

14-73 

994 

2 

14.20 

1239 

2 

14.16 

714 

2 

14-35 

848 

I 

14.42 

995 

2 

14.14 

1240 

2 

13.83 

741 

I 

14.02 

851 

3 

14.48 

IOOI 

I 

14.89 

1264 

I 

14.01 

747 

2 

15.17 

852 

3 

14-51 

1003 

I 

13.96 

1265 

2 

13.99 

15-39 

860 

14.87 

IOIO 

2 

14.69 

1266 

15.03 

769 

14.49 

868 

14.87 

1028 

I 

14.21 

1267 

13.70 

771 

14.69 

875 

13.87 

1029 

I 

14.21 

1294 

14.48 

774 

14.48 

884 

14.92 

1039 

I 

14.62 

1300 

13.98 

775 

13.96 

885 

14.08 

1040 

I 

14.41 

1327 

14.22 

813 

14.92 

886 

15.06 

1053 

I 

14-57 

1349 

14.24 

8i5 

I3.6l 

892 

13.80 

1054 

I 

14-37 

1381 

14.46 

816 
817 

14.54 
14.36 

893 
917 

2 
I 

14-43 
14.88 

1064 
1066 

2 

I 

15.22 
14.52 

1396 
1397 

14.65 
14.06 

818 

15.01 

944 

2 

15.10 

1067 

3 

14.90 

1398 

15-10 

819 

2 

14-45 

946 

I 

14.14 

1070 

i 

13-50 

1412 

14.38 

830         2 

14-35 

966 

2 

14-75 

1072 

I 

14.47 

1444 

14-33 

[Zone  g=  15°  to  20°.            Mean  Diurnal  Motion  =  14.18°  ±  0.028.] 

23 
46 

4 

4 

14.06° 
14.15 

320 

338 

I 
I 

15.21° 
14-34 

797 
808 

i 
i 

14-31° 
13.60 

1140 
1146 

I 

14-57° 
14.07 

58' 

I 

15-47 

339 

4 

14.28 

809 

i 

13.19 

1147 

14.07 

70 

I 

14.58 

380 

i 

13-15 

810 

i 

14.11 

H55 

12.94 

77 

I 

14.58 

492 

2 

14-59 

863 

3 

14.56 

11  79 

14.71 

68 

3 

14.26 

493 

I 

14.68 

900 

i 

14.01 

1186 

14.21 

83 

5 

13.97 

494 

I 

14.68 

905 

I 

14-75 

1188 

14.11 

77' 

2 

14-37 

497 

I 

14.46 

906 

I 

15.26 

1212 

2 

13.48 

89 

2 

I3-8I 

506 

I 

13.72 

913 

i 

13-74 

1219 

3 

13.84 

90 

4 

13-88 

509 

2 

13.56 

938 

3 

14.46 

1206 

2 

14.64 

101 

3 

13-81 

2 

13-65 

939 

3 

14-50 

1225 

I 

13-71 

108' 
108 

5 

2 

13.55 
13.42 

1 

I 
I 

14.27 
13-95 

940 
951 

4 
i 

14.08 
14-95 

1252 
1258 

2 
I 

13.73 
14.42 

118' 

4 

13-57 

570 

3 

13-93 

952 

i 

14-95 

1309 

2 

14.28 

in 

2 

14.40 

613 

i 

13.96 

979 

i 

13.32 

1312                        14.27 

112 

2 

13-89 

614 

i 

14.27 

1042 

2 

14.85 

1313 

14-57 

108" 

2 

15-27 

642 

i 

14.09 

1043 

2 

14.25 

I3l6 

14-37 

143 

I 

14.21 

700 

2 

14-35 

1055 

I 

14.26 

1317 

14-57 

134 

I 

14.29 

723 

14.22 

1056 

I 

13.96 

1318 

14-75 

208 

I 

14.40 

728 

13.92 

1081 

3 

14.27 

1319 

14.14 

236 

2 

14.72 

729 

13-31 

HOI 

2 

14.60 

1325 

13.68 

240 

2 

14.87 

730 

13.89 

1  102 

4 

14.42 

1338 

13-94 

241 

2 

14-77 

736 

14-32 

H03 

2 

14.04 

1340 

14.04 

254 

2 

13-73 

759 

14.60 

1107 

4 

14.33 

1348 

13-94 

244' 

2 

13-68 

766 

14.78 

1108 

2 

13.62 

1401 

2 

14-35 

273 

4 

14.01 

778 

14.40 

1123 

4 

13.76 

1417 

4 

13-70 

281 

5 

13.72 

787 

2 

14.30 

1126 

2 

13.68 

I4l8 

3 

14-04 

301 

4 

14.38 

788 

2 

14.41 

1134 

I 

14.07 

1420 

i 

13-75 

306 

3 

14-13 

789 

2 

13-65 

1138 

I 

14.38 

1426      :      2 

14.44 

319 

i 

14.67 

794 

I 

13-93 

1  139 

I 

14-57 

1430             I 

13-79 

44  THE   ROTATION    PERIOD    OF    THE    SUN    AS    DETERMINED 

TABLE  2.    Diurnal  Motions  Corresponding  to  each  Five-Degree  Zone. — Continued. 


[Zone  h  —  —15°   to  —20°.            Mean  Diurnal  Motion  =  14.32°  ±  0.031.] 

Diurnal 

Diurnal 

Diurnal 

Diurnal 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal  . 

14 

I 

I3.780 

256 

4 

13.84° 

563 

4 

13.55° 

849 

3 

I4.570 

15 

2 

13.89 

257 

I 

14.94 

573 

I 

14.88 

855 

3 

14.27 

26 

I 

12.54 

262 

I 

15.79 

583 

I 

13.31 

864 

I 

15.23 

47' 

4 

14.22 

266 

I 

15.71 

584 

I 

14.51 

867 

I 

15.14 

49 

3 

14.64 

271 

I 

13-86 

590 

I 

14-33 

870 

4 

14.37 

47" 

2 

13.29 

276 

5 

14.08 

594 

I 

13-93 

890 

4 

14.40 

62 

4 

14.66 

280 

5 

14.08 

607 

2 

14.50 

887 

2 

14.65 

62' 

I 

13.65 

283 

3 

14.42 

603 

I 

I4.6l 

965 

I 

13.73 

79' 

2 

14.11 

284 

3 

13.63 

611 

I 

I4.IO 

1002 

I 

14.52 

80 

2 

14.17 

290 

2 

14.58 

637 

I 

13-79 

1004 

I 

14.80 

49' 

2 

14.74 

291 

2 

14-57 

655 

I 

14.30 

ion 

2 

14.74 

80" 

I 

13.56 

292 

2 

14.58 

658 

I 

14.50 

1025 

I 

14.41 

H3 

2 

13.89 

310 

I 

I4.O2 

668 

I 

14.80 

1027 

I 

14.52 

114 

2 

14.10 

329 

4 

14.09 

679 

3 

14.71 

1041 

I 

14.52 

136 

2 

14-37 

331 

4 

14.04 

680 

2 

14.52 

1048 

2 

14.48 

150 

2 

13.84 

333 

i 

14.92 

681 

3 

13.93 

1078 

I 

13-44 

150' 

2 

14-54 

345 

3 

13-66 

683 

3 

14.13 

1194 

3 

14.62 

156 

2 

15.84 

346 

3 

14.06 

684 

2 

15.14 

1196 

2 

14.47 

155 

2 

14.25 

391 

i 

13.42 

689 

I 

15.29 

1261 

2 

I4.8I 

150" 

13.23 

393 

i 

13.24 

715 

2 

14.30 

1271 

14.67 

174 

15.11 

473 

i 

14.67 

716 

2 

14-35 

1273 

15.13 

175 

13-86 

481 

3 

14.56 

718 

2 

14.68 

1288 

14.48 

176 

14.15 

482 

3 

14.54 

734 

14.13 

1324 

14.12 

211 

14.40 

490 

3 

14.57 

752 

I3.8I 

1350 

13.74 

212 

14.50 

513 

2 

13.85 

753 

14.38 

1413 

13.83 

210 

2 

14.21 

528 

I 

14.09 

755 

I4.6O 

1433 

14.18 

226 

6 

14.25 

529 

I 

13.67 

831 

14.35 

1434 

14.58 

235 

2 

14.36 

525 

2 

14.14 

834 

14.36 

1442 

14-45 

238 

5 

14.19 

534 

2 

14-39 

835 

14.64 

1443 

14.09 

239 

i 

14.74 

556 

3 

14-34 

837 

4 

14.57 

1445 

13.85 

245 

2 

14.78 

56i 

2 

13-86 

838 

5 

14-39 

1447 

14.69 

247 

2 

14-49  ; 

562 

I 

14.62 

[Zone  t  =  20°  to  25°.            Mean  Diurnal  Motion  =  14.16°  ±  0.038.] 

3 

3 

14.59° 

224 

2 

14.23° 

696 

I4.I40 

1174 

13.72° 

6 

2 

14.29 

231 

I 

15.65 

697 

14.26 

ii75 

14.01 

4 

2 

14.71 

275 

4 

13-66 

756 

14.72 

1225 

I3.7I 

29 

2 

14.49 

336 

i 

14.07 

757 

14.60 

1259 

14.31 

30 

2 

14.06 

337 

i 

I3.56 

763 

14-59 

1260 

14.72 

30' 

I 

14.66 

340 

i 

12.94 

777 

2 

13.38 

1283 

14.56 

29' 

I 

14.66 

375 

i 

I3.8I 

2 

14.03 

1305 

13.29 

83' 

I 

13-65 

376 

i 

14-59 

80^ 

I 

14.21 

1307 

13.27 

90' 

3 

13-80 

377 

i 

14-59 

806 

I 

14.11 

1310 

14-37 

90" 

i 

13-87 

383 

i 

14.67 

900 

I 

14.01 

1311 

14.27 

118 

6 

13.62 

384 

i 

I3.8I 

908 

I 

I3.6l 

1314 

14.17 

no 

4 

14.18 

389 

i 

13.90 

926 

I 

14.31 

1320 

13.88 

89' 

2 

14-57 

495 

3 

14.10 

941 

2 

14.60 

1328 

13.34 

121' 

2 

14.25 

498 

i 

13.89 

942 

2 

14-95 

1330 

13.01 

135 

3 

13.91 

54i 

3 

13.71 

980 

2 

13.84 

1346 

14-34 

137 

I 

14.57 

540 

2 

13.91 

1089 

I 

I4.06 

1385 

2 

14.05 

139 

2 

14.24 

582 

2 

15-79 

1119 

3 

13.86 

1386 

2 

14.15 

140 
140' 

3 

13.31 
14.76 

549 
612 

3 

i 

14-35 
14.56 

1127 
1128 

2 
2 

14.07 
13-97 

1387 
1388 

2 
2 

13.70 
14.56 

206 

3 

13-93 

621 

i 

14-77 

1144 

I 

13.08 

1402 

I 

15.00 

214 

3 

14.44 

676 

i 

15.10 

1150 

2 

14.06 

1389 

2 

14.40 

215 

3 

14.25 

i 

FROM    THE    MOTIONS    OF   THE    CALCIUM    FLOCCULI.  45 

TABLE  2.    Diurnal  Motions  Corresponding  to  each  Five-Degree  Zone. — Continued. 


[Zone  /==  —  20°   to  —  25°.            Mean  Diurnal   Motion  =  14.12°  ±  0.042.] 

Diurnal 

Diurnal 

Diurnal 

Diurnal 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

No. 

Days. 

motion, 
sidereal. 

II 

I 

12.67° 

102' 

2 

14-69° 

462 

3 

14.43° 

665 

13.90° 

22 

3 

12.07 

1  60' 

I 

13.94 

463 

I 

14.22 

666 

13.90 

47 

3 

13.71 

160 

3 

13.24 

502 

I 

14-35 

667 

14.40 

45 

3 

14.10 

180 

13.86 

503 

I 

14.55 

691 

14.71 

59 

3 

13.63 

187 

14.48 

536 

I 

14.39 

692 

14.37 

59' 

2 

I4.OO 

1  88 

13-55 

543 

2 

14.39 

706 

2 

14.35 

63' 

2 

13.93 

189 

I4.O6 

591 

3 

14.56 

7i7 

2 

14.40 

65 

3 

14.07 

190 

13.73 

597 

2 

14.15 

836 

4 

14-45 

69 

3 

13.40 

237 

5 

I4.I8 

598 

2 

14.50 

847 

I 

14.64 

ft 

80' 
69' 

3 

2 

I 
I 

14.66 

14-43 
14.03 
I4.I8 

239 
246 
267 
269 

i 

4 
3 
i 

14.74 
14.43 
14.69 
13.86 

604 
605 
606 
648 

I 
I 
I 

I 

13.13 
12.36 
1440 
14.51 

856 
858 

86 

3 

14.17 

14.34 
14.70 
14.17 

94 

4 

14.12 

270 

3 

14.32 

656 

I 

14.40 

888 

14.50 

95 

4 

14.08 

278 

2 

14.19 

657 

I 

14.90 

889 

14.22 

97 

6 

13.91 

279 

2 

14.52 

661 

I 

14.00 

1117 

13-68 

96' 

4 

14.42 

274 

2 

14.67 

662 

I 

14.30 

1296 

14.78 

97' 

i 

13.97 

332 

I 

14.64 

663 

I 

13.90 

1297 

14-68 

102 

4 

14.00 

392 

I 

12-53 

664 

I 

14.30 

1400 

13.69 

US 

2 

14.04 

[Zone  k  =  25°   to  30°.            Mean  Diurnal   Motion  =  13.74°  ±  0.062.] 

3' 

3 

13.64°! 

221 

2 

13.09° 

542 

2 

I3.8I0 

927 

i 

I4.220 

6' 

2 

14.07 

222 

2 

12.  80 

575 

I 

13.24 

1091 

i 

15.29 

181 

I 

13-55 

334 

I 

14.07 

685 

2 

14.35 

II2O 

2 

13.82 

i95 

I 

13-33 

335 

I 

13.14 

687 

2 

14-43 

1286 

I 

13-53 

196 

I 

13.46 

517' 

I 

12.75 

698 

I 

14.03 

1322 

I 

13.94 

199 

I 

13.36 

532 

3 

14.27 

803 

I 

14.21 

1332 

I 

13.78 

200 

3 

13.07 

539 

3 

14.10 

804 

I 

14.00 

1409 

I 

14.27 

213 

i 

13-49 

550 

I 

13.73 

909 

3 

13.09 

1410 

I 

13.51 

220 

2 

13-37 

i 

[Zone   /  =  —  25°    to  —  30°.            Mean   Diurnal   Motion  =  13.95°  ±  0.082.] 

8 

2 

12.61° 

171 

4 

14.05° 

47i 

i 

14.09° 

651             I 

13.79 

8' 

I 

12.  6l 

171' 

i 

15.30 

508 

i 

14.02 

652 

I 

13.57 

16 

2 

13.54 

i 

14.48 

504 

i 

15.34 

659 

I 

13.80 

16' 

2 

13.19 

186 

i 

13.60 

537 

2 

14.30 

660 

I 

14.30 

38' 

I 

13.09 

250 

2 

13.96 

538 

I 

14.10 

707 

2          14.88 

38"  1     5 

14.35 

255 

2 

14.29 

544 

2 

13.98 

770 

2 

13.60 

45" 

I           14.62 

293 

2 

14.98 

545 

2 

14.79 

857 

I 

14.52 

6/ 

4     '•   14-39 

294 

2 

14-73 

546 

2 

13.29 

1399 

2 

14.15 

96          4 

14.33 

388 

I 

H.53 

616 

I 

13.56 

1414 

I 

13.83 

152          i 

13.10 

465 

I 

13.81 

617 

I 

13.56 

[Zone    m  =  30°    to   35°.            Mean    Diurnal    Motion  =  13.60°  ±  0.069.] 

197 

I 

13.55° 

686 

2 

13-88° 

i  1023 

2 

13-35° 

1323 

I           13.85° 

I 

13.82 

800 

I 

13.60 

1090 

I 

13.53 

1329 

i     !  13.89 

288 

2 

14.57 

802 

I 

13.60 

1263 

I 

13.60 

1356 

3     i  13.67 

517 

2 

13.40      |    1022 

2 

12.82 

1285 

I 

12.73 

1357 

3        13-99 

569 

I 

13.43  ; 

[Zone  w  =  3o°   to  —  35°.            Mean   Diurnal  Motion  ==  13.79°  —  0.124.] 

64 

3 

14.26° 

153 

4 

14.10° 

464 

I 

I3.8I0 

626 

i 

12.84° 

64" 

i 

13.91 

157 

2 

14.96 

466 

I 

12.76 

653 

i 

13.98 

151 

2 

13.96 

170 

I 

13.23 

610 

I 

14.29 

1406 

2 

13.35 

THE   ROTATION    PERIOD    OF    THE   SUN    AS    DETERMINED 


DISTRIBUTION  AND  AREAS  OF  THE  FLOCCULI. 

No  very  minute  flocculi  were  measured  in  this  investigation.  The  best- 
defined  points,  which  showed  the  least  change  from  day  to  day,  were  selected 
for  measurement.  In  many  cases  these  points  were  chosen  in  the  outlying 
portions  of  large  groups  of  flocculi;  in  others  they  represented  the  centers 
of  smaller  compact  masses.  In  all  cases,  however,  the  measures  relate  to  the 
coarser  flocculi.  They  therefore  afford  no  evidence  as  to  the  motions  of 
those  minute  flocculi,  not  exceeding  a  second  of  arc  in  diameter,  which  are 
shown  on  the  best  plates  obtained  with  the  Rumford  spectroheliograph  or  the 
5-foot  spectroheliograph  of  the  Mount  Wilson  Solar  Observatory. 

The  approximate  distribution  and  area  of  the  principal  flocculi  on  the  Sun 
during  the  period  of  this  investigation  were  determined  as  follows:  The 
globe,  as  already  stated,  is  ruled  with  meridians  and  parallels  i°  apart,  the 
10°  lines  being  strengthened.  In  the  squares  thus  formed,  10°  on  a  side, 
the  areas  of  the  flocculi  were  estimated  by  counting  the  number  of  i° 
squares  covered  by  them.  A  sample  record  for  the  first  plate  is  given  below. 

TABLE  3. 


Longitude. 

Latitude. 

East  of  central  meridian. 

West  of  central  meridian. 

Total  in 

—  30  to  —  20 

—  20  tO  —  IO 

—  10  too 

o  to  10 

10  tO  20 

20  tO  30 

zone. 

40°  to     30° 

3 

7 

9 

o 

3 

3 

0 

25 

30               20 

4 

II 

17 

"5 

4 

8 

2 

46 

20                10 

2 

4 

8 

1 

i 

3 

I 

IQ 

10                  0 

4 

4 

i 

6 

4 

i 

2 

16 

0°  tO  -10° 

6 

2 

5 

fi 

c 

3 

i 

I 

18 

—  10           —2O 

7 

3 

4 

0 

i 

14 

5 

34 

—  2O           —30 

4 

4 

14 

17 

10 

10 

59 

-30        -40 

0 

i 

5 

I 

2 

6 

15 

East. 

West. 

Only  a  limited  area  of  the  globe  was  used,  but  the  results  obtained  from 
the  considerable  number  of  plates  employed  should  be  fairly  representative. 
The  last  column  of  the  above  table  gives  the  total  area  of  the  flocculi  in  each 
10°  zone.  In  table  4  these  results  are  brought  together,  and  the  grand  total 
for  each  zone  is  given.  These  totals  have  supplied  the  data  for  platting  the 
curve  shown  in  fig.  4.  The  curve  at  the  opposite  limb  of  the  Sun  on  this 
plate  shows  the  number  of  the  flocculi  in  the  various  zones  measured  in 
determining  the  rotation  periods.  The  scale  of  the  ordinates  of  this  curve 
is  i  inch  to  250  points  measured. 

It  should  be  remembered  that  in  view  of  the  varying  density  and  contrast 
of  the  plates,  and  the  great  range  of  brightness  of  the  flocculi,  such  estimates 


FROM    THE    MOTIONS    OF   THE    CALCIUM    FLOCCULI.  47 

of  areas  are  necessarily  very  rough.  They  may  serve,  however,  to  give  an 
idea  of  the  distribution  of  the  flocculi  measured,  and  the  approximate  area 
occupied  by  them. 

N 


Distribution  of  points 
in  floccuU  measured  for 
rotation  periods. 


Areas,  in,  square  d&jrees, 

covered  by  flocculi. 
&•  ^ 


FIG.  4.    DISTRIBUTION  AND  AREAS  OF  THE  FLOCCULI. 


TABLE  4.    Areas  of  the  Flocculi. 


Plate 
No. 

+40 

to 

+30 

+30 

to 

+20 

+  20 

to 

+  10 

+10 

to 
o 

0 

to 

—  10 

—  IO 

to 

—20 

20 

to 

-30 

—30 
to 
—40 

Plate 

No. 

+4o 
to 

+30 

+30 
to 

+20 

+80 

to 

+  10 

+10 

to 
o 

0 

to 

—  IO 

—  10 

to 

—  20 

—  20 

to 
-3° 

—3o 

to 
—40 

2401 

25 

46 

19 

16 

18 

34 

59 

15 

3204 

8 

19 

42 

6 

41 

13 

I 

I 

*2407 

^207 

8 

28 

GO 

181 

60 

7 

*TV/ 

2421 

20 

33 

44 

18 

21 

08 

40 

8 

O  v/ 

3211 

7 

20 

27 

68 

31 

216 

81 

/ 

5 

2429 

16 

5i 

66 

29 

76 

63 

83 

9 

3214 

2 

II 

20 

57 

27 

159 

58 

i 

2442 

7 

67 

25 

77 

221 

57 

8 

3216 

0 

6 

25 

108 

51 

47 

27 

5 

2452 

5 

15 

84 

21 

80 

238 

40 

14 

3218 

6 

IO 

43 

85 

19 

50 

34 

3 

2465 

2 

19 

125 

22 

64 

214 

08 

15 

3221 

4 

8 

36 

30 

28 

22 

2 

2471 

9 

20 

138 

13 

62 

77 

15 

3223 

i 

n 

31 

26 

29 

124 

27 

I 

2482 

7 

15 

112 

12 

58 

86 

79 

14 

3228 

6 

21 

32 

23 

36 

123 

12 

I 

2496 

5 

18 

III 

30 

18 

10 

60 

7 

3232 

2 

12 

25 

17 

43 

130 

13 

I 

2501 

i 

22 

94 

55 

31 

43 

38 

3239 

II 

23 

20 

27 

16 

25 

7 

0 

2521 

5 

37 

109 

44 

40 

114 

29 

8 

3241 

8 

29 

50 

32 

19 

18 

14 

2 

2542 

i 

29 

37 

13 

8 

78 

23 

i 

3245 

16 

16 

53 

23 

22 

5 

7 

0 

2558 

o 

24 

22 

12 

20 

3 

0 

3247 

6 

13 

92 

40 

20 

13 

4 

0 

2560 

i 

25 

33 

22 

8 

27 

14 

2 

3253 

9 

22 

57 

44 

31 

37 

7 

I 

2569 

0 

II 

39 

28 

13 

66 

16 

17 

3258 

6 

20 

59 

35 

24 

46 

4 

5 

2580 

3 

9 

5 

6 

24 

108 

63 

22 

3265 

3 

9 

16 

28 

23 

29 

10 

i 

2588 

3 

9 

n 

17 

3i 

185 

104 

39 

3272 

12 

20 

29 

44 

41 

36 

2 

0 

2500 

5 

33 

35 

37 

29 

173 

141 

36 

3279 

9 

21 

46 

60 

22 

19 

2 

0 

2598 

6 

64 

17 

9 

5 

29 

32 

12 

3284 

5 

18 

42 

77 

24 

35 

4 

0 

2617 

n 

82 

16 

4 

13 

I 

3286 

0 

II 

63 

47 

30 

IOO 

16 

2 

2619 

4 

39 

22 

7 

18 

68 

15 

5 

3293 

7 

16 

66 

64 

49 

no 

58 

I 

2628 

I 

15 

68 

9 

47 

123 

40 

4 

3295 

9 

19 

55 

35 

16 

53 

24 

O 

2634 

0 

4 

86 

8 

41 

172 

6 

3300 

12 

14 

39 

112 

19 

47 

32 

I 

2639 

i 

6 

106 

13 

42 

138 

82 

3 

3303 

4 

7 

30 

117 

21 

48 

ii 

3 

2651 

3 

15 

72 

17 

52 

56 

14 

3308 

5 

17 

66 

119 

30 

32 

8 

2 

2675 

8 

14 

40 

30 

22 

58 

26 

13 

33io 

4 

12 

58 

85 

38 

61 

12 

0 

2681 

7 

27 

63 

21 

102 

IOI 

32 

14 

3315 

6 

15 

36 

49 

57 

136 

16 

2 

2694 

5 

34 

53 

26 

73 

51 

24 

2 

3319 

i 

0 

15 

40 

64 

144 

9 

0 

2699 

2 

8 

21 

16 

68 

171 

33 

3 

3320 

16 

31 

43 

59 

34 

136 

9 

2 

2712 

9 

28 

33 

24 

61 

80 

n 

6 

3326 

23 

25 

34 

47 

86 

12 

6 

*2722 

3333 

22 

31 

126 

19 

13 

12 

6 

i 

2741 

5 

7 

48 

43 

18 

7 

12 

7 

3338 

13 

22 

no 

22 

35 

22 

5 

0 

2756 

6 

17 

25 

7 

16 

n 

16 

i 

3348 

39 

57 

88 

35 

46 

23 

12 

I 

2787 
2791 

2 
0 
2 

4 

IO 

5 

12 

18 

15 

42 
38 
29 

22 
20 

38 

32 
34 

52 

29 
44 
38 

9 
14 

7 

3354 

?M 

16 
16 

10 

43 
44 
24 

64 
67 

40 
26 
28 

35 
34 

20 

2O 
17 
14 

33 
44 
38 

3 

5 

2 

2797 

6 

13 

33 

18 

30 

18 

7 

3374 

7 

27 

35 

27 

II 

14 

2 

0 

2800 

2 

10 

21 

14 

25 

71 

21 

7 

3382 

12 

22 

82 

57 

31 

36 

15 

5 

2809 

6 

15 

16 

7 

27 

112 

6 

0 

3388 

5 

23 

129 

H3 

23 

33 

23 

i 

2812 

3 

13 

II 

7 

13 

III 

n 

6 

3394 

0 

6 

89 

88 

27 

43 

34 

4 

28l8 

9 

66 

25 

27 

13 

35 

34 

5 

3398 

3 

9 

95 

92 

24 

77 

35 

9 

2821 

7 

78 

90 

38 

16 

33 

21 

6 

3405 

13 

17 

69 

73 

15 

27 

12 

0 

2829 

5 

61 

132 

17 

^ 

68 

12 

8 

5 

16 

75 

61 

14 

47 

8 

5 

2831 

4 

25 

105 

25 

6 

63 

16 

8 

3417 

9 

20 

68 

60 

37 

83 

13 

4 

2839 

2 

9 

67 

6 

7 

58 

II 

10 

3424 

20 

28 

35 

21 

52 

14 

2 

2870 

4 

9 

3 

n 

14 

48 

13 

6 

3429 

18 

14 

25 

114 

18 

43 

28 

6 

2877 

i 

5 

4 

14 

13 

46 

17 

6 

3439 

30 

33 

49 

127 

24 

22 

4 

2 

2880 

i 

4 

4 

13 

n 

46 

18 

6 

3441 

24 

29 

56 

116 

38 

24 

25 

2 

*2888 

3447 

ii 

23 

21 

18 

27 

36 

18 

2 

2898 

i 

30 

72 

6 

21 

23 

12 

14 

O*T*T/ 

3453 

18 

—*o 

32 

40 

25 

30 

«_/w 

25 

8 

I 

2904 

2 

18 

60 

45 

29 

22 

16 

9 

3456 

16 

38 

42 

12 

II 

17 

9 

3 

3020 

0 

5 

17 

14 

24 

54 

25 

14 

3462 

17 

32 

32 

17 

24 

22 

12 

4 

3028 

I 

2 

60 

13 

27 

59 

23 

24 

3464 

13 

21 

25 

13 

23 

26 

6 

2 

3062 

2 

12 

22 

27 

14 

63 

44 

3 

3467 

19 

22 

99 

90 

37 

18 

21 

2 

3069 

6 

29 

26 

12 

15 

44 

32 

3 

I  3473 

n 

25 

104 

67 

13 

2O 

20 

5 

3079 

4 

2O 

19 

12 

10 

46 

22 

5 

3476" 

13 

28 

41 

21 

13 

69 

10 

4 

3082 
3093 

i 

2 

II 
23 

II 
27 

10 

55 

9 
31 

33 

24 

44 

7 

2 

!  3479 
|  348i 

14 

12 

18 
23 

21 
19 

18 

12 

n 
16 

63 

8 

14 

3 
5 

3101 

I 

7 

47 

69 

74 

40 

6 

3488 

15 

27 

23 

36 

66 

27 

12 

8 

3104 

6 

6 

73 

23 

26 

15 

n 

3 

3493 

14 

28 

17 

33 

64 

41 

23 

10 

3106 

3 

12 

103 

18 

38 

19 

6 

0 

3498 

13 

32 

22 

43 

55 

36 

15 

14 

3112 

i 

14 

32 

21 

46 

22 

IO 

i 

3503 

9 

15 

27 

17 

16 

16 

6 

3H7 

0 

4 

50 

21 

55 

24 

7 

2 

3507 

IO 

19 

49 

24 

10 

17 

8 

4 

3121 

0 

2 

31 

15 

30 

22 

16 

6 

3509 

8 

18 

49 

32 

14 

22 

10 

3 

3185 

8 

20 

IOI 

40 

36 

32 

32 

7 

2 

15 

37 

45 

14 

26 

20 

3 

3190 

0 

22 

138 

30 

56 

15 

7 

i 

3528 

3 

9 

25 

24 

13 

27 

16 

4 

3191 

10 

29 

85 

30 

T  C 

45 

23 

18 

M 

2 

3533 

4 

16 

34 

14 

19 

9 

5 

3201 

10 

17 

42 

J5 
II 

29 

II 

I 

I 

Total 

987 

3519 

6772 

4827 

4073 

8576 

3529 

738 

*  Not  measured. 


FROM    THE    MOTIONS   OF   THE   CALCIUM    FLOCCULI.  49 

DISCUSSION  OF  THE  RESULTS. 

The  mean  values  of  the  diurnal  motion  for  each  zone  of  5°,  with  the  com- 
puted probable  errors  and  the  weights,  are  brought  together  in  the  following 
table.  The  weighted  means  for  corresponding  zones  in  north  and  south 
latitudes,  together  with  their  probable  errors,  are  also  included. 

TABLE  5. 


* 

North. 

£ 

Weight. 

South. 

Weight. 

Weighted  mean. 

o°  to  5° 
5        10 

14.  72°  ±0.03  1 
14.50       .027 

156 

196 

I4.570  ±0.045 
14-55           .030 

103 

2O2 

14.66°  ±0.026 
14.52           .020 

10        15 

14.34        .024 

208 

14.39           .020 

323 

14.37           .Ol6 

15           20 

14.14       .025 

222 

14.30           .028 

240 

14.22           .019 

20          25 

14-13        .035 

143 

14.11           .038 

144 

14.12           .026 

25        30 

13.74       .060 

51 

14.03           .073 

66 

I3.OO           .049 

30        35 

13.64        .073 

26 

13.93           -120 

20 

13.76           .067 

A  comparison  of  these  results  with  those  of  Carrington,  Spoerer,  and 
Maunder  for  spots,  StratonofT  for  the  faculae,  and  Duner  and  Halm  for  the 
reversing  layer  (iron  lines),  is  given  in  fig.  5.  Numerical  comparisons  are 
also  given  in  the  following  pages.  Before  proceeding  to  these  comparisons, 
it  should  be  remarked  that  the  large  proper  motions  of  the  calcium  flocculi 
must  always  stand  in  the  way  of  very  accurate  results,  unless  a  much  greater 
number  of  observations  than  those  here  included  are  available. 


27.5 
27.0 
2*5 
26.0 
25.5 
25.0 
245 
24.0  ; 

FIG. 

/ 

//, 

f 

\ 

7 

j. 

TJ 

V 

/ 

// 

.,- 

-'" 

/ 

/ 

f 

^ 

T/ 

/ 

s 

^\ 

/ 

>•*' 

+  ^  ' 

J 

'    . 

X 

I, 

--/, 

.... 

,„' 

* 

/ 

,. 

?* 

X 

i  / 

X 

s 

, 

/ 

sS' 

' 

/ 

/ 

/  _^ 

^ 

/ 

-?'* 

^ 

A 

./?- 

..- 

•;/•; 

>'' 

^ 

-^ 

*<?- 

'^ 

/ 

''^ 

./ 

X 

s* 

^ 

^ 

*' 

•y 

:..^' 

-*-  — 

~^? 

gz.. 



s' 

—  n 
—  F< 

acculi 
culae 

s^ 

'>" 

" 

— 



—  & 

n  sp< 
in  8P< 

>ts(Ca 
rts(Sp 

•ring* 

oerer 

n) 

.3 

—  — 



—  R 
—  R 

•versii 
sver»ii 

^lay 
I?'«Y 

r(Dun8'r) 
sr(  Halm  190 

-02) 

- 

—  R 

.verai, 

**y 

ir(H«|m  19( 

3) 

>°                 &'                W               13°               ZO"              25*               30°               35*              40*              45°               « 

5.    THE  ROTATION  OF  THE  SUN  AS  SHOWN  BY  THE  MOTIONS  OF  THE  SPOTS,  FACUL 
FLOCCULI,  AND  REVERSING  LAYER. 

50 


THE    ROTATION    PERIOD    OF    THE    SUN    AS    DETERMINED 


As  the  result  of  a  long  series  of  Sun-spot  observations,  Spoerer  derived 
the  following  empirical  formula,  as  best  representing  the  diurnal  motion  of 
the  spots  in  any  latitude: 

£  =  8.548°  +  5.798°  cos  </> 

Computing  the  values  of  £  corresponding  to  <f>  =  2.5°,  7.5°,  12.5°,  etc.,  and 
comparing  the  results  with  those  we  have  obtained  for  the  calcium  flocculi, 

we  have: 

TABLE  6. 


0 

Spoerer, 
spots 

£ 

Flocculi. 

£ 

Flocculi 
minus 
spots. 

o°to    5° 

14-34° 

14.66° 

0.32° 

5        10 

14.30 

14.52 

0.22 

10        15 

14.21 

14-37 

0.16 

15            20 

14.08 

14.22 

0.14 

20           25 

13.90 

14.12 

0.22 

25            30 

13.69 

13.90 

0.21 

30        35 

13.44 

13.76 

0.32 

According  to  Spoerer's  results,  it  would  thus  appear  that  the  flocculi  move 
more  rapidly  across  the  disk  than  the  spots.  The  gain  in  24  hours,  taking 
the  mean  without  regard  to  latitude,  is  about  0.2°. 

However,  this  conclusion  is  not  borne  out  by  Mr.  and  Mrs.  Maunder's 
extensive  investigation  of  the  Greenwich  Sun-spot  measures  for  the  two 
complete  cycles  i879-i9Oi.10  The  results  of  this  investigation,  for  the  zones 
covered  by  our  observations,  are  given  in  the  following  table: 

TABLE  7. 


0 

Greenwich 
spots. 

Flocculi. 

Flocculi 
minus 

£ 

f 

spots. 

2.5° 

14.61° 

14.66° 

0.05° 

7.5 

14.50 

14.52 

0.02 

12.5 

14.44 

14.37 

-0.07 

17.5 

14.38 

14.22 

—  0.16 

22.5 
27.5 

14.14 
13.78 

14.12 
13.90 

—  0.02 
O.I2 

32.5 

14.07 

13.76 

-0.31 

StratonofFs  study  of  the  solar  rotation  is  based  upon  the  measurement  of 
the  heliographic  positions  of  faculse  photographed  at  Pulkowa,  during  the 
years  1891-94."  Wilsing  had  previously  investigated  this  subject,  with  the 
aid  of  photographs  made  at  Potsdam  in  1884,  and  found  for  the  faculae  a 
velocity  of  14.27°  in  24  hours,  constant  for  all  latitudes.  This  unexpected 
result  caused  Belopolsky  to  attack  the  problem.  Although  he  measured  only 
a  small  number  of  photographs,  he  was  able  to  detect  the  fact  that  the 

"  The  Solar  Rotation  Period  from  Greenwich  Sun-spot  Measures  from  1879-1901." 
Monthly  Notices,  June,  1905. 

11  Stratonoff :  "  Sur  le  Mouvement  des  Facules  Solaires."  Memoir es  de  V Academic 
Imperiale  des  Sciences  de  St.-Petersbourg,  VIII  Serie,  1896. 


FROM    THE    MOTIONS    OF   THE    CALCIUM    FLOCCULI. 


51 


faculae  in  high  latitudes  rotate  in  a  longer  period  than  the  spots  at  the  equator. 
Stratonoff,  with  a  much  larger  amount  of  material  at  his  disposal,  undertook 
to  determine  the  law  of  rotation  of  the  faculae  as  a  function  of  the  latitude. 
2,245  measures  were  made  of  1,062  faculae  on  234  plates.  As  it  was  never 
possible  to  follow  a  facula  more  than  four  days  from  the  limb,  the  measures 
were  necessarily  made  on  the  least  favorable  part  of  the  solar  surface.  In 
spite  of  this  fact  the  following  very  satisfactory  results  were  obtained.  Our 
corresponding  values  for  the  flocculi  are  given  for  comparison. 

TABLE  8. 


* 

North. 
I 

No.  of 
obser- 
vations. 

South. 
I 

No.  of 
obser- 
vations. 

Faculae,  means. 

s 

Flocculi,  means. 

Faculae 
minus 
flocculi. 

0°  to  <5° 

14.62° 

Q 

14  62°  ±0.127° 

14  66°  ±o  026° 

—o  04° 

5  10 
10  15 

15  20 
20  25 
25  30 

30  35 

-zc  40 

T";: 

14.61 

14.34 
14.14 

14.21 

13.97 
13-50 

39 
125 
no 

124 
109 
15 

14-63° 
14.26 
14.21 
14.17 
I4.2O 
13.65 

n.6i 

6? 

124 
137 

101 

34 

24 

14.61  ±0.061 
14.31  ±0.044 
14.18  ±0.036 
14.19  ±0.036 
14.08  ±0.040 
13.60  ±0.059 
13.61  ±0.086 

14.52    ±0.020 

14.37  ±0.016 

14.22    ±O.OI9 
14.12    ±0.026 
13.90    ±0.049 
13.76    ±0.067 

0.09 
—  0.06 
—  O.O4 
O.07 

0.18 
—  0.16 

It  appears  from  the  table  that  the  observed  differences  in  the  daily  motion 
of  the  faculse  and  flocculi  are  of  the  same  order  as  the  probable  errors,  except 
in  the  higher  latitudes,  where  the  observations  are  few  and  the  results 
uncertain. 

Let  us  now  consider  whether  the  daily  motion  of  the  flocculi  decreases  at  a 
uniform  rate  in  passing  from  the  equator  toward  high  latitudes.  For  com- 
parison, we  also  include  StratonofFs  results  for  the  faculae.  The  quantities 
in  the  columns  A£  are  obtained  by  subtracting  the  value  of  £  for  each  zone 
from  the  value  of  £  in  the  zones  +5°  — 5°,  which  we  take  as  the  standard 
velocity. 

TABLE  9. 


Faculae. 

Flocculi. 

North. 

South. 

Mean. 

North. 

South. 

Mean. 

5°  to  io° 

0.01° 

0.01° 

0.01° 

0.16° 

0.11° 

0.14° 

10       15 

0.28 

0.36 

0.31 

0.32 

0.27 

0.29 

15          20 

0.48 

0.41 

0.44 

0.52 

0.36 

0.41 

20          25 

0.41 

o.35 

0.43 

0.53 

0.55 

0.54 

25       30 

0.65 

0.42 

0.54 

0.92 

0.63 

0.76 

30       35 

•31:          AQ 

1.  12 

0.97 

I  01 

1.02 
I  01 

i.  02 

o.73 

0.89 



It  thus  appears  that  the  acceleration  is  very  nearly  uniform.  Indeed,  the 
entire  series  may  be  fairly  well  represented  by  a  straight  line,  since  the 
larger  deviations  can  be  given  little  weight,  as  they  correspond  to  zones  in 
which  few  observations  are  available. 


52 


THE   ROTATION    PERIOD    OF   THE    SUN    AS    DETERMINED 


An  interesting  investigation  of  the  rotation  period  of  the  Sun,  based  upon 
the  motion  of  large  groups  of  faculse,  is  that  of  Wolfer."  He  found  that 
during  the  period  in  question  (1887-90)  there  were  two  persistent  groups 
of  faculae,  of  great  size,  on  the  Sun,  about  180°  apart  in  longitude.  Each 
group  showed  a  gradual  increase  in  longitude,  which  continued  during  the 
entire  period.  As  the  longitudes  were  based  upon  Spoerer's  mean  daily 
value  of  14.2665°,  derived  from  observations  of  the  spots,  it  follows  that  the 
faculae  were  moving  more  rapidly  than  the  spots,  if  we  may  assume  that 
Spoerer's  mean  daily  value  can  be  depended  upon.  Maunder's  results,  how- 
ever, as  already  remarked,  throw  doubt  on  this  point  and  the  question  can  not 
at  present  be  regarded  as  settled. 

Let  us  now  compare  our  results  for  the  flocculi  with  those  of  Duner  for 
the  reversing  layer.  Duner's  determination  of  the  solar  rotation  was  made 
by  measuring  the  double  displacement  of  two  iron  lines,  A  6301.72  and 
A  6302.72,  referred  to  neighboring  telluric  lines.  The  radial  velocities  found 
for  different  latitudes  therefore  represent  the  motion  of  the  iron  vapor  in 
the  reversing  layer.  Duner's  observations  correspond  to  the  latitudes  0.4°, 
JS-O0,  30-i °j  45-0°,  60.0°,  and  75.0°.  In  order  to  obtain  velocities  corre- 
sponding to  the  mean  latitudes  of  our  zones,  Duner's  formula  II,  adapted 
from  Spoerer's  formula  for  the  spots,  has  been  used.13  The  values  of  £  have 
thus  been  obtained  by  substituting  2.5°,  7.5°,  12.5°,  17.5°,  22.5°,  27.5°,  and 
32.5°  for  <£  in  the  formula: 

|  =  8.564°  +6.153°  cos  <£ 
TABLE  10. 


0 

Reversing  layer. 

Flocculi,  means. 
§ 

Reversing  layer 
minus  flocculi. 

o°to  5° 

I4.7I0 

14.66° 

0.05° 

5       10 

14.66 

14.52 

0.14 

10       15 

14-57 

14-37 

0.20 

15          20 

14.43 

14.22 

0.21 

20         25 

14.25 

14.12 

0.13 

25       30 

14.02 

13.90 

0.12 

30       35 

13.75 

13.76 

—  0.01 

So  far  as  can  be  judged  from  this  comparison,  in  all  latitudes  excepting 
the  highest,  which  is  of  low  weight  in  the  flocculi  determinations,  the 
reversing  layer  gives  higher  velocities  than  the  calcium  flocculi,  the  average 
difference  in  the  value  of  £  amounting  to  about  0.014°.  Since  the  corre- 
sponding difference  in  the  case  of  Spoerer's  spots  is  about  0.2°,  and  of 
opposite  sign,  the  Sun  would  appear  to  have  a  gradually  increasing  rotational 
velocity  in  the  order  spots,  faculae  and  flocculi,  reversing  layer,  were  it  not 
for  Maunder's  results. 

13  A.  Wolfer:  "  Zur  Bestimmung  der  Rotationszeit  der  Sonne,"  V.  J.  S.  d.  zurch. 
naturforsch.  Ges.,  Bd.  41. 

13  Astronomische  Nachrichten,  No.  3994. 


FROM    THE    MOTIONS    OF    THE    CALCIUM    FLOCCULI. 


53 


It  is  an  interesting  question  whether  the  apparently  greater  velocity  of  the 
iron  vapor  in  the  reversing  layer,  as  compared  with  the  faculse  and  flocculi, 
is  genuine.  The  average  results  of  Halm's  observations,  covering  the  period 
1901-06,  would  point  to  a  contrary  conclusion.  They  are  given  in  the 
following  table,  extracted  from  his  more  complete  table  in  Astronomische 
Nachrichten,  No.  4146. 

TABLE  n. 


0 

Linear 
velocity. 

No.  of 
obser- 
vations. 

Daily 
motion. 
1 

0 

Linear 
velocity. 

No.  of 
obser- 
vations. 

Daily 
motion. 
£ 

2.3° 

2.042  km< 

103 

14.55° 

21.4° 

.856  im- 

43 

14.19° 

6.6 

2.032 

09 

14.56 

24.5 

.788 

55 

13.98 

9.4 

2.OO2 

65 

14.44 

27.6 

•755 

53 

14.09 

12.4 

1.972 

44 

14.37 

30-7 

.657 

4i 

13.72 

15-6 
18.4 

1.952 
1.907 

8 

14.42 
14.31 

.596 
.561 

45 
5i 

13-59 
I3.8I 

These  results  differ  decidedly  from  DuneYs,  especially  in  the  lower  lati- 
tudes (see  fig.  5).  It  may  be  added,  however,  that  an  unpublished  series 
of  measures  by  Adams,  covering  the  period  June  1906  to  February  1907, 
gives  results  in  very  close  agreement  with  Duner's,  up  to  a  latitude  of  45°. 
Beyond  this  point  the  reductions  are  not  yet  complete.  The  very  high  pre- 
cision of  Adams's  measures  lends  great  weight  to  his  confirmation  of  Duner's 
results." 

We  do  not  attempt  to  discuss  here  the  unsettled  question  of  a  possible 
variation  in  the  rotational  velocity  of  the  Sun,  indicated  by  Halm's  measures 
for  1901-02  and  1903.  The  apparently  high  accuracy  of  Halm's  results 
appears  favorable  to  his  conclusions,  but  it  must  remain  for  the  future  to 
prove  whether  such  variations  actually  occur. 

It  can  not  be  said  from  the  comparisons  given  above  that  a  systematic 
difference  of  velocity  of  various  classes  of  solar  phenomena  has  been  demon- 
strated. So  far  as  the  flocculi  are  concerned,  no  very  general  discussion  of 
their  motions  could  be  based  on  the  restricted  materials  now  available.  We 
are  both  engaged  in  work  with  powerful  instruments,  which  furnish  larger 
solar  photographs,  much  richer  in  detail  and  better  suited  for  measurement 
than  the  Kenwood  plates.  We  accordingly  expect  to  return  to  this  discussion, 
with  the  advantage  afforded  by  a  longer  series  of  better  observations.  A 
more  general  consideration  of  the  problem  of  the  solar  rotation,  and  a  more 
accurate  estimate  of  the  weight  to  be  attached  to  measurements  of  the 
velocity  of  various  classes  of  phenomena,  should  then  be  practicable. 

14  Since  this  paper  was  put  in  type  the  following  articles  on  the  solar  rotation  have 
appeared  in  Contributions  from  the  Mount  Wilson  Solar  Observatory,  Nos.  20,  24,  and  25. 

Spectroscopic  Observations  of  the  Rotation  of  the  Sun.  By  Walter  S.  Adams. 
Astrophysical  Journal,  XXVI,  November,  1907. 

Preliminary  Note  on  the  Rotation  of  the  Sun  as  Determined  from  the  Displacements 
of  the  Hydrogen  Lines.  By  Walter  S.  Adams.  Astrophysical  Journal,  XXVII,  April,  1908. 

Preliminary  Note  on  the  Rotation  of  the  Sun  as  Determined  from  the  Motions  of 
the  Hydrogen  Flocculi.  By  George  E.  Hale.  Astrophysical  Journal,  XXVII,  April,  1908. 


54  THE  ROTATION  PERIOD  OF  THE  SUN. 

FUTURE  STUDIES  OF  THE  SOLAR  ROTATION.          > 

A  general  attack  on  the  problem  of  the  solar  rotation  calls  for  the  co-oper- 
ation of  several  observatories.    It  should  include: 

1 i )  Further  investigations  of  the  motions  of  individual  spots,  closely  con- 

nected with:  (a)  simultaneous  determinations  of  their  level,  made 
with  the  spectroheliograph;  (b)  their  appearance  at  and  near  the 
limb  (visibility  of  umbra,  etc.),  also  bearing  upon  the  question  of 
level;  (c)  their  spectra,  including  general  absorption,  and  relative 
intensity  of  lines,15  bearing  on  their  temperature  and  level ;  (d) 
measures  of  the  solar  activity,  particularly  in  the  zone  occupied  by 
the  spots  in  question. 

(2)  A  continuation  of  Maunder 's  work  on  spot  motions. 

(3)  A  continuation  of  StratonofFs  work  on  the  motions  of  the  faculse, 

using  such  means  of  increasing  contrast  as  will  permit  the  inclusion 
of  faculse  near  the  center  of  the  Sun. 

(4)  Investigations  with  the  spectroheliograph  on  the  motions  of  (a)  the 

bright  regions  photographed  with  the  Ht  or  K±  lines ;  (b)  the  H2 
or  K2  calcium  flocculi;  (c)  if  possible,  the  H3  or  K3  dark  calcium 
flocculi;  (d)  the  hydrogen  flocculi;  (e)  the  iron  flocculi,  and  those 
of  other  gases. 

(5)  A  continuation  and  extension  of  the  spectroscopic  work  of  Duner  and 

Halm,  on  the  motion  in  the  line  of  sight  of  the  reversing  layer  at 
opposite  limbs  of  the  Sun.  This  investigation,  which  would  neces- 
sarily require  the  co-operation  of  several  observatories,  should  pro- 
vide for  the  employment  of  certain  lines  in  common  by  all  observers. 
It  should  also  involve  the  use,  by  each  observer,  of  certain  additional 
lines,  chosen  so  as  to  include:  (a)  a  considerable  number  of  lines  in 
the  spectrum  of  at  least  one  substance ;  (b)  lines  representing  ele- 
ments of  high,  medium,  and  low  level;  (c)  lines  enhanced  in  the 
spark,  and  those  strengthened  at  low  temperatures. 

(6)  An  investigation  of  the  motion  in  the  line  of  sight  of  the  lower 

chromosphere  (or  reversing  layer),  through  spectroscopic  observa- 
tions of  the  relative  displacements  of  bright  lines  at  opposite  limbs 
of  the  Sun. 

(7)  A  determination  of  the  motion  in  the  line  of  sight  of  quiescent  promi- 

nences, in  various  latitudes  and  at  various  heights  above  the  limb. 

SUMMARY. 

This  investigation  of  the  motion  of  the  calcium  flocculi  has  led  to  the 
following  conclusions : 

1.  The  rotation  periods  for  different  latitudes  show  the  existence  of  an 

equatorial  acceleration,  similar  to  that  previously  observed  in  the  case 
of  Sun-spots,  faculse,  and  the  reversing  layer. 

2.  In    approximate   terms,    the    acceleration   varies    uniformly    with    the 

latitude. 

3.  The  average  daily  motion  of  the  calcium  flocculi  is  of  the  same  order  as 

that  of  the  spots,  faculse,  and  reversing  layer.  The  differences  among 
the  rotation  periods  obtained  by  various  observers  are  so  marked  that 
no  definite  conclusions  can  yet  be  drawn  as  to  the  relative  velocities 
of  these  different  phenomena. 

"See  Hale,  Adams,  and  Gale.     "Preliminary  Paper  on  the  Cause  of  the  Charac- 
teristic Phenomena  of  Sun-Spot  Spectra."    Astrophysical  Journal,  October,  1906. 


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